Plasma film forming system

ABSTRACT

In a plasma film forming apparatus, two first electrodes  51  connected to a power source  4  and two grounded second electrodes  52  are arranged in the order of the second electrode  52 , the first electrode  51 , the first electrode  51  and the second electrode  52 . A first flow passage  50   a  formed between the central first electrodes  51  allows a raw material gas (first gas) for being formed into a film to pass therethrough. A plasma discharge space  50   b  of a second flow passage formed between the first and second electrodes  51, 52  on the both sides allows an excitable gas (second gas) to pass therethrough, which excitable gas is exited by plasma such that the raw material can be formed into a film, but that the excitable gas itself is merely excited but not formed into a film. Those gases are converged at a crossing part  20   c  between the first and second flow passages and blown off via a common blowoff passage  25   a . By this, the apparatus composing members such as electrodes can be prevented from being adhered with a film.

TECHNICAL FIELD

This invention relates to a plasma surface processing technique, inwhich a processing gas is plasmatized by impressing an electric fieldbetween a pair of electrodes, processing such as film formation,etching, ashing, cleaning, surface modification or the like is executedwith respect to the surface of a base material of a semiconductor basematerial or the like. More particularly, the invention relates to anapparatus suited for the so-called remote-control type in which a basematerial is arranged away from an electric field impressing spacebetween electrodes of a base material, in a plasma film formingapparatus.

BACKGROUND ART

The plasma surface processing apparatus is provided with a pair ofelectrodes (for example, Japanese Patent Application Laid-Open No.H11-236676). A processing gas is introduced between the pair ofelectrodes and an electric field is also impressed therebetween togenerate a glow discharge. By this, the processing gas is plasmatized.The processing gas thus plasmatized is blown to the surface of a basematerial of a semiconductor base material or the like. By this, suchprocessing as film formation (CVD), etching, ashing, cleaning andsurface modification can be conducted with respect to the surface of thebase material.

The number of electrodes provided to a single apparatus is not limitedto two. For example, in a plasma processing apparatus disclosed inJapanese Patent Application Laid-Open No. H05-226258, a plurality ofelectrodes are arranged such that their polarities are alternatelyappeared.

A plasma surface processing system includes a so-called direct system inwhich a base material is disposed in an electric field impressing spacebetween a pair of electrodes, and a so-called remote type in which abase material is disposed away from an electric field impressing spaceand a processing gas plasmatized in the electric field impressing spaceis blown to this base material. It further includes a low pressureplasma processing system in which the entire system is put into apressure reducing chamber and processing is conducted in a lowerpressure circumstance, and a normal pressure processing system in whichprocessing is conducted under pressure (generally normal pressure) closeto atmospheric pressure.

For example, as disclosed in Japanese Patent Application Laid-Open No.H11-251304, the remote type normal pressure surface processing apparatuscomprises a blowoff nozzle for blowing out a processing gas. Within thisnozzle, a pair of electrodes are arranged in opposing relation. At leastone of the electrodes is provided at an opposing surface thereof with asolid dielectric layer such as ceramic by thermally sprayed coatingfilm. This arrangement is made in order to prevent the occurrence of arcdischarge occurrable in a normal pressure interelectrode space. Thenozzle is formed with a blowoff passage which is continuous with theelectric field impressing space between the electrodes. The basematerial is disposed ahead of this blowoff passage.

The gas to be used for plasma surface processing is selected dependingon the purpose of processing. In case of film formation (CVD), gascontaining the raw material of film is used. This raw material gas isintroduced between the electrodes and reacted with plasma to form a filmon the surface of a base material.

However, this film formation processing technique has such a problemthat the film, which is originally intended to be adhered to the basematerial, is liable to adhere to the apparatus side. Particularly, inthe remote type, the gas is readily adhered to the surface of theelectrode before it is blown off from the blowoff passage. The gas isalso readily adhered to the peripheral area of the blowoff passage ofthe nozzle or to the opposing surface of the nozzle with respect to thebase material. This results in loss of an increased amount of rawmaterial. Maintenance such as replacement of electrodes, etc. andcleaning thereof is more frequently required. Total replacement of themain component such as electrodes means significant waste of thecomponent materials. Moreover, it is extremely troublesome to totallyclean the nozzle in order to remove the adhesion (stain) adhered to theperipheral area of the blowoff passage. In addition, the processing mustbe temporarily stopped during the maintenance.

Incidentally, Japanese Patent Application Laid-Open No. H03-248415discloses a technique in which in the normal pressure CVD, in general,the wall surface from the peripheral area of the nozzle to its dischargepart is composed of a wire netting and an inert gas is blown off throughthe meshes of the wire netting, thereby to prevent the film fromadhering to the apparatus side. This techniques, however, again has sucha problem that the flow of processing gas is disturbed by the inert gascoming through the meshes, thus badly degrading the film formationefficiency onto the base material.

Moreover, the normal pressure plasma surface processing has such aproblem that an average free travel (life span) of the radicals is shortcompared with the lower pressure circumstance. For this reason, if thenozzle is arranged too away from the base material, it becomes unable toform a film due to deactivation. On the other hand, if the nozzle isarranged too close to the base material, arc is liable to occur betweenthe electrode on the side to which the electric field is impressed andthe base material, and the base material gets, in some instances,damaged.

In the normal pressure plasma surface processing, arc (abnormal electricdischarge) may occur at the rear surface (reversed side surface of theopposing surface) of the electrode and at the edge of the electrode.This occurs particularly significantly when rare gas including argon orhydrogen is used as processing gas.

The present invention has been made in view of the above situation. Itis, therefore, an object of the present invention to provide a techniquefor solving the problem of film adhesion to the electrodes, etc., at thetime of plasma film formation, particularly at the time of plasma filmformation according to the remote type, of all the plasma surfaceprocessing. It is another object of the present invention to provide atechnique capable of conducting a favorable film formation processingwhile preventing the arc discharge.

DISCLOSURE OF INVENTION

In order to solve the above-mentioned problems, according to a firstfeature of the present invention, there is provided a plasma filmforming apparatus for forming a film on a surface of a base materialunder the effect of plasma, comprising:

-   (A) a first gas supplying source containing a raw material of the    film;-   (B) a second gas supplying source caused by plasma discharge to    reach an excited state but containing no component capable of being    formed into the form of film; and-   (C) a processing head which is to be placed opposite the base    material;

the processing head being provided with:

-   (a) a grounded ground electrode; and-   (b) an electric field impressing electrode connected to an electric    power source and forming a plasma discharge space between the ground    electrode and the electric field impressing electrode;

the processing head being formed with:

-   (c) a first flow passage for introducing a first gas from the first    gas supplying source to the base material in such a manner as to    avoid or pass very near the plasma discharge space; and-   (d) a second flow passage including the plasma discharge space and    for causing a second gas coming from the second gas supplying source    to contact the first gas after allowing the second gas to pass    through the plasma discharge space.

Owing to the above arrangement, film can be prevented from adhering tothe surfaces of the electrodes which constitute the plasma dischargespace. Thus, loss of the raw material can be reduced. Moreover, thetrouble of maintenance such as replacement and cleaning of theelectrodes can be reduced.

In the first feature, it is accepted that, for example, the first andsecond flow passages are converged with each other and continuous with acommon blowoff passage which is open to a surface of the processing headwhich surface is to be placed opposite the base material (see FIG. 3, aswell as elsewhere). It is also accepted that downstream ends of thefirst and second flow passages are spacedly open to a surface of theprocessing head which surface is to be placed opposite the basematerial, and the open ends serve as a blowoff port for the first gasand as a blowoff port for the second gas, respectively (see FIG. 11, aswell as elsewhere). In the former common blowoff construction, the firstgas and the plasmatized second gas can be contacted in the commonblowoff passage so as to be reacted reliably. In the latter individualblowoff construction, film can surely be prevented from being formed onthe inner peripheral surface of the blowoff passage.

In the common blowoff construction, for example, one of the first andsecond flow passages is linearly continuous with the common blowoffpassage, and the other is crossed with the above-mentioned one flowpassage at an angle. One of the first and second gases can be linearlyflown in the blowoff direction and the other gas can be convergedthereto.

The crossing angle between the first and second flow passages in thecommon blowoff construction is, for example, right angle. However, thecrossing angle is not limited to this but it may be an obtuse angle oran acute angle. Both the first and second flow passages may be angledwith respect to the common blowoff passage.

In the first feature, for example, the electrodes are provided as amember for defining the first flow passage. Owing to this arrangement,the specific first flow passage forming member can be omitted or madeshort.

In the first feature, for example, the processing head is provided withtwo electrodes which have the same polarities and which are arranged inmutually adjacent relation, and the first flow passage is formed betweenthe electrodes having the same polarities. The electrodes having thesame polarities may refer to the electric field impressing electrodes,or they may be the ground electrodes.

In the first feature, for example, the processing head is provided withtwo each of the electric field impressing electrodes and groundelectrodes, thus four in total, the two electric field impressingelectrodes are arranged in mutually adjacent relation thus forming thefirst flow passage therebetween, and the two each electric fieldimpressing electrodes are placed opposite the two each correspondingground electrodes thus forming the plasma discharge space therebetween(see FIG. 3, as well as elsewhere).

The four electrodes are arranged, for example, in the order of theground electrode, the electric field impressing electrode, the electricfield impressing electrode and the ground electrode, and owing to thisarrangement, the two plasma discharge spaces and thus the second flowpassages are arranged on both sides with the single first flow passagesandwiched therebetween.

In this four-electrode and three-flow passage construction, for example,the processing head includes a base material opposing member which is tocover a surface to be faced with the base material of the electrode, andthe base material opposing member formed with respective blowoffpassages of the three flow passages (see FIG. 11). Owing to thisarrangement, one mode of the individual blowoff construction isconstituted.

Moreover, in the four-electrode and three-flow passage construction, itis accepted that the processing head includes a base material opposingmember which is to cover a surface to be faced with the base material ofthe electrode, a communication passage is formed as a part of the secondflow passage between the base material opposing member and each electricfield impressing electrode, the plasma discharge space and the firstflow passage is communicated with each other through the communicationpassage, and the base material opposing member is formed with a commonblowoff passage of the first and second gases such that the commonblowoff passage is continuous with a crossing part between the firstflow passage and the communication passage (see FIG. 3). Owing to thisarrangement, one mode of the individual blowoff construction isconstituted.

The base material opposing member is composed, for example, of aninsulative (dielectric) material such as ceramic.

As a more generalized construction of the four-electrode and three flowpassage construction, it is accepted that the processing head isprovided with a plurality of electric field impressing electrodes and aplurality of ground electrodes, and the electrodes are arranged inparallel relation such that first flow passages each formed between theelectrodes having the same polarities and plasma discharge spaces, i.e.,second flow passages each formed between the electrodes having differentpolarity are alternately arranged (see FIG. 13). The terms “electrodeshaving the same polarities refer to the electric field impressingelectrodes or refer to ground electrodes, and the terms “electrodeshaving different polarities” refer to the electric field impressingelectrode and the ground electrode.

In this first and second flow passages alternately arrangedconstruction, it is preferable that the electrodes located at oppositeend parts in the arrangement direction are ground electrodes. Owing tothis arrangement, electric field can be prevented from leaking outsideof the row of electrodes.

In the alternately arranged construction, the first and second flowpassages may be arranged alternately one by one, or one group by onegroup. The first group consists of the first flow passage(s) and thesecond group consists of the second flow passage(s). The second flowpassages and the first flow passages may be arranged alternately suchthat only one first flow passage is arranged after a plurality of secondflow passages. In the alternative, they may be arranged alternately suchthat a plurality of first flow passages are arranged after only onesecond flow passage. One group of the first or second flow passages maybe different in number in accordance with the arranging direction.Preferably, the number of the second flow passages is larger, as awhole, than that of the first flow passages. Owing to this arrangement,sufficient reaction of the raw material gas can be obtained.

In the first feature, for example, the electric field impressingelectrode and the ground electrode extend in a direction orthogonal tothe opposing direction of the electric field impressing electrode andthe ground electrode, an upstream end of the plasma discharge spacebetween the electrodes is disposed at one end part in a first directionorthogonal to the opposing direction and extending direction, and adownstream end thereof is disposed at the other end part in the firstdirection. Owing to this arrangement, the range can be enlarged in whicha film can be formed at a time and the processing efficiency can beenhanced.

In the elongate electrode construction, it is preferable that anelectricity feed line to the electric field impressing means isconnected to one end part in the longitudinal direction of the electricfield impressing electrode, and a ground line is connected to the otherend part in the longitudinal direction of the ground electrode (see FIG.6). Owing to this arrangement, the electricity feed line and the groundline can be prevented from being short-circuited.

In one preferred mode of the first feature, the ground electrode isarranged in opposing relation on the side of the electric fieldimpressing electrode which is to be faced with the base material in theprocessing head (see FIG. 15). Owing to this arrangement, arc can beprevented from occurring between the electric field impressing electrodeand the base material by interposing the ground electrode between theelectric field impressing electrode and the base material. Thus, thebase material can be prevented from being damaged, and the processinghead and thus, the plasma discharge space can be located sufficientlyclose to the base material. As a result, the active pieces can surely bebrought to the base material before the active pieces lose activity, anda high-speed and favorable film forming processing can be conducted.This interposing construction is particularly effective for thegenerally normal pressure plasma film formation processing in which anaverage free travel of radicals (distance until the active pieces loseactivity) is short.

The terms “generally normal pressure (close to atmospheric pressure)”used herein refers to a range from 1.333×10⁴ to 10.664×10⁴ Pa.Particularly, a range from 9.331×10⁴ to 10.397×10⁴ Pa is preferablebecause pressure adjustment becomes easy and the construction of theapparatus becomes simplified.

In the ground electrode interposing construction, for example, theprocessing head includes a base material opposing member which is tocover a surface to be faced with the base material of the electric fieldimpressing electrode, and the ground electrode is disposed at the basematerial opposing member. A gap is formed between the electric fieldimpressing electrode and the base material opposing member, and the gapserves as a second flow passage including the plasma discharge space. Itis preferable that the plasma discharge space is directly crossed withthe first flow passage, and the base material opposing member is formedwith a common blowoff passage of the first and second gases such thatthe common blowoff passage is continuous with the crossing part.According to this directly converging construction, the plasma in thedischarge space can be overflowed to the crossing part. By thisoverflowed part, the first gas can directly be plasmatized (the firstgas can pass very near the plasma discharge space). Owing to thisarrangement, the film forming efficiency can be enhanced.

In the ground electrode interposing construction, for example, thereceiving recess for receiving the ground electrode is formed in asurface (surface on the reversed side of the electric field impressingside) to be faced with the base material of the base material opposingmember. Owing to this arrangement, the ground electrode is directlyfaced with the base material. In this ground electrode directly opposingconstruction, it is preferable that the base material opposing member iscomposed of ceramic, and a forming part for forming the receiving recessof the base material opposing member is provided as a solid dielectriclayer which is to cover a metal main body of the ground electrode. Owingto this arrangement, it is no more required to provide a specific soliddielectric layer to the ground electrode.

In the ground electrode interposing construction, for example, an endface to be faced with the common blowoff passage of a metal main body ofthe electric field impressing electrode may be generally flush with (seeFIG. 20) or more expanded than an end face on the same side of the metalmain body of the electric field impressing electrode. It is alsoaccepted that an end face on the side facing with the common blowoffpassage of the metal main body of the ground electrode is more retractedthan an end face on the same side of the metal main body of the electricfield impressing electrode (see FIG. 21). In the former generally flushor expanded construction, the electric field can surely be preventedfrom leaking to the base material side from the ground electrode, arccan surely be prevented from falling onto the base material, and thedistance between the processing head and the base material can surely bereduced. In the latter retracted construction, a lateral electric fieldcan be formed between the end faces of the electric field impressingelectrode and the ground electrode, and the reaction space for the firstgas can be located closer to the base material.

In the first feature, for example, the processing head is provided witha grounded conductive member such that the grounded conductive membercovers a side to be faced with the base material of the electric fieldimpressing electrode (FIGS. 15 and 23, as well as elsewhere). Owing tothis arrangement, arc can be prevented from occurring between theelectric field impressing electrode and the base material by interposingthe grounded conductive member between the electric field impressingelectrode and the base material. Thus, the base material can beprevented from being damaged, and the processing head and thus, theplasma discharge space can be located sufficiently close to the basematerial. As a result, the active pieces can surely be brought to thebase material before the active pieces lose activity, and a high-speedand favorable film forming processing can be conducted. This interposingconstruction is particularly effective for the generally normal pressureplasma film formation processing in which the average free travel of theradicals (distance until the active pieces lose activity) is short.

In this conductive member interposing construction, it is accepted thatthe conductive member forms a plasma discharge space between theelectric field impressing electrode and the conductive member, and theconductive member is provided as the ground electrode (see FIG. 15).Owing to this arrangement, the conductive member can also serve as theground electrode and thus, the number of parts can be reduced.

In the conductive member interposing construction, an insulative memberfor insulating the conductive member and the electric field impressingelectrode may be filled between the insulative member and the electricfield impressing electrode (see FIG. 23). Owing to this arrangement,electric discharge can be prevented from occurring between theconductive member and the electric field impressing electrode.

In the first feature, it is preferable that the processing head isprovided with an intake duct having an intake port surrounding aperipheral edge part of a base material opposing surface thereof. Owingto this arrangement, the processed gas can be prevented from remainingin the space and discharged smoothly. Eventually, stain adhered to thebase material opposing member can be reduced, and the frequency ofmaintenance can be reduced. Moreover, the flow of the first and secondgases can be stabilized in the space between the processing head and thebase material, and a generally laminar flow state can be attained.

According to a second feature of the present invention, there isprovided a plasma film forming apparatus for forming a film on a surfaceof a base material under the effect of plasma, comprising:

-   -   a first gas supplying source containing a raw material of the        film;    -   a second gas supplying source caused by plasma discharge to        reach an excited state but containing no component for capable        of being formed into the form of film;    -   a grounded ground electrode;    -   an electric field impressing electrode connected to an electric        power source and forming a plasma discharge space in such a        manner as to oppose the ground electrode;    -   a first flow passage forming means for flowing therethrough a        first gas from the first gas supplying source in such a manner        as to avoid or pass very near the plasma discharge space and        blowing the first gas to the base material; and    -   a second flow passage forming means for allowing a second gas        coming from the second gas to pass through the plasma discharge        space and causing the second gas to contact the first gas. Owing        to this arrangement, film can be prevented from adhering to the        surfaces of the electrodes which constitute the plasma discharge        space. Thus, the raw material loss can be reduced. Moreover, the        trouble of maintenance such as replacement of the electrodes and        cleaning thereof can be reduced.

As mentioned above, the electrodes having the same polarities can be thefirst flow passage forming means, and the electrodes having differentpolarities can be the second flow passage forming means. That is, it isaccepted, for example, that the electric field impressing electrodeincludes a surface forming a first flow passage and provided as thefirst flow passage forming means. Moreover, it is also accepted that theelectric field impressing electrode and the ground electrode areprovided as the second flow passage forming means, in which a secondflow passage and thus, a plasma discharge space are formed between theelectric field impressing electrode and the ground electrode.

According to another mode of the second feature, the ground electrode isarranged on the side to be faced with the base member of the electricfield impressing electrode with a dielectric member (insulative member)sandwiched between the ground electrode and the electric fieldimpressing electrode, and a cutout for allowing the dielectric member tobe exposed therethrough is formed in a part of the ground electrode, theinside of the cutout serves as the plasma discharge space; the secondflow passage forming means makes the second gas blow out along theground electrode and enter the cutout; and the first flow passageforming means makes the first gas blow out on the reverse side to theground electrode from the second gas in such a manner as to form alaminar flow with the second gas (see FIG. 22). Owing to thisarrangement, the first gas can be flown in such a manner as to pass verynear the plasma discharge space and reacted nearer to the base material.Moreover, the film adhesion to the apparatus side can be restrained.

In a plasma surface processing (particularly normal pressure surfaceprocessing) as in the present invention, a solid dielectric layer forpreventing the occurrence of arc (abnormal electric discharge) isprovided to at least one of the opposing surfaces of the electric fieldimpressing electrode and the ground electrode. This solid dielectriclayer may be coated on the metal main body of the electrode by thermallysprayed coating or the like (see FIG. 3). In the alternative, it may beof a dielectric case receiving structure as described hereinafter.

That is, the electrode of the plasma film forming apparatus of thepresent invention may comprise a main body composed of metal, and adielectric case composed of a solid dielectric member for receivingtherein the main body (FIG. 19). Owing to this arrangement, even if afilm (stain) should be adhered to the electrode, it would be adheredonly to the dielectric case and would not be adhered to the electrodemain body. Therefore, simply by cleaning only the dielectric case, themain body can be used as it is. Moreover, since the entire electrodemain body is covered with the dielectric case as the solid dielectriclayer, abnormal electric discharge can be prevented from occurring notonly at the opposing surface with respect to the other electrode butalso at the rear surface and the edge. Particularly, even in case suchsubstance easy to discharge as argon or hydrogen is used as theprocessing gas, abnormal electric discharge can surely be prevented fromoccurring at the rear surface, etc. Moreover, it is easy to applyvariation to the thickness compared with the technique in which thesurface of the electrode main body is directly coated by thermallysprayed coating or the like. The dielectric case receiving constructionitself can be applied not only to the plasma film formation whichbelongs to the field of the present invention but also widely to otherplasma surface processing electrode construction such as cleaning,etching, ashing, surface modification and the like. It can be appliednot only to the remote type plasma processing but also to direct type.

Preferably, the dielectric case includes a case main body retractablyreceiving the electric main body in an internal space whose one surfaceis open, and a lid for covering the opening.

Both the paired electric field impressing electrode and the groundelectrode may be of the dielectric case receiving construction. In thatcase, the plasma discharge space of the second flow passage is formedbetween the dielectric case of the electric field impressing electrodeand the dielectric case of the ground electrode.

It is accepted that each of the two electrodes having same polaritiesand forming the first flow passage comprise a main body composed ofmetal and a dielectric case composed of a solid dielectric member forreceiving therein the main body, the dielectric cases of the electrodesare placed opposite each other, thereby forming the first flow passagetherebetween.

The dielectric cases of the electrodes may be separately formed, or theymay be integrally connected to one another (see FIG. 28, as well aselsewhere). In the former separate construction, maintenance such asreplacement can be conducted individually depending on the status ofadhesion (stain). In the latter integral construction, the number ofparts can be reduced. In addition, relative positioning and the like ofthe electrodes can be conducted easily and correctly. In case of theintegral construction, it is preferable that a gas flow passage isformed in the case main body, and receiving spaces for receiving theelectrode main body therein are formed on both sides with this flowpassage sandwiched therebetween. It is accepted that the sectional areaof this flow passage is varied along the gas flowing direction such thatthe passage becomes gradually narrow or wide, or it is provided with astep. Owing to this arrangement, the pressure and speed of the gas flowcan be changed. According to the integral construction, such a deformedflow passage as just mentioned can be formed easily.

It is accepted that each electrode and thus the dielectric case thereofextend in a direction orthogonal to the opposing direction with respectto the other electrode, and the dielectric case integrally includes agas uniformizing part for uniformly dispersing gas, which is introducedinto a flow passage between the dielectric case and the other electrode,in the extending direction (see FIG. 30). Owing to this arrangement, anadditional member of uniformizing gas is not more required, and thenumber of parts can be reduced.

The thickness of a plate part on the side forming the plasma dischargespace in the dielectric case may be different between the upstream sideand the downstream side of the plasma discharge space (see FIG. 28).Moreover, in the case integral construction, it is accepted that theintegral dielectric case is formed with a second flow passage serving asthe plasma discharge space, a metal main body is received in each sideof the integral dielectric case with the flow passage sandwichedtherebetween, and a distance between the metal main bodies is differentbetween the upstream side and the downstream side of the plasmadischarge space (see FIG. 29). Owing to this arrangement, manyvariations can be applied to the status of plasma by varying the mannerfor generating the radical species as it flows. Thus, the surfaceprocessing recipe can be enriched.

It is accepted that each electrode comprises a metal-made main body anda solid dielectric layer disposed at least at the plasma discharge spaceforming surface of the main body, and the thickness of the soliddielectric layer at the plasma discharge space forming surface isdifferent between the upstream side and the downstream side of theplasma discharge space. It is also accepted that each electrodecomprises a metal-made main body and a solid dielectric layer disposedat least at the plasma discharge space forming surface of the main body,and a distance between the two electrodes is different between theupstream side and the downstream side of the plasma discharge space.

As means for impressing electric field to the electrodes or as groundingmeans of the present invention, a feed or grounding pin may be used, ora covered conductor may be connected directly to the electrode.

In the former pin construction, the pin includes a conductive pin mainbody having a pin hole opening to a tip end face thereof andwithdrawably embedded in the electrode, a core member electricallyconnected with the pin main body and slideably received in the pin hole,and a spring received in the pin hole and for biasing the core member soas to be pushed out of the tip end opening of the pin hole (see FIG.10). Owing to this arrangement, the pin and the electrode can surely beelectrically conducted. Moreover, since the power feed pin can bewithdrawn from the electrode, it cannot be any interference at the timeof maintenance.

In the latter covered conductor construction, it is preferable that aconductor hole is formed in the electrode, the covered conductor isinserted in the conductor hole, the covered conductor is formed bycovering a conducting wire with an insulative material, only a tip partof the wire located on an inner side of the hole is exposed from theinsulative material, a screw is screwed in the electrode in such amanner as to be generally orthogonal to the conductor hole, and thescrew presses the exposed tip part of the wire against an innerperipheral surface of the conductor hole (FIG. 24). Owing to thisarrangement, the conductive tip part can surely be fixed to theelectrode main body. Moreover, abnormal electric discharge can surely beprevented from occurring at the pulled-out part of the conductor fromthe electrode. At the time of maintenance, the conductor can easily bewithdrawn from the electrode by loosening the screw.

In the first feature, it is preferable that the processing headremovably includes a base material opposing member formed with a firstand a second gas blowoff passage and disposed opposite the base material(see FIG. 9). Owing to this arrangement, even if a film (stain) shouldbe adhered to the base material opposing surface of the processing head,etc., only the base material opposing member can be separated. Then,only the base material opposing member can be cleaned by being dippedinto a chemical liquid such as, for example, strong acid. Therefore, itis no more required to bring the entire processing head to the cleaningprocess, and the maintenance can be simplified. Moreover, by preparing aspare part of the base material opposing member, the surface processingcan be kept continued even during the time of maintenance.

The removing construction itself of the base material opposing membercan be applied not only to the plasma film formation which belongs tothe field of the present invention but also widely to other plasmasurface processing head such as cleaning, etching, ashing, surfacemodification and the like. Moreover, it can also be applied to othersurface processing heads than plasma such as thermal CVD.

In the opposing member removing construction, it is preferable tofurther comprise support means for supporting the base material opposingmember in such a manner as to place a peripheral edge part of the basematerial opposing member thereon with a surface to be faced with thebase material of the base material opposing member directing downward;an upper side part from the base material opposing member of theprocessing head being integrally placed on the base material opposingmember. Moreover, it is preferable that the support means has aframe-like configuration so that the processing head can be receivingtherein in such manner as to be able to be removed upward, and an innerflange for hooking on a peripheral edge part of the base materialopposing member is disposed at an inner peripheral edge of a lower endpart of the support means. Owing to this arrangement, simply by pullingup the processing head, the base material opposing member can beseparated at the time of maintenance. Moreover, a processing headdirecting downward is constituted and the base material is disposedbeneath the head.

In the opposing member removing construction, it is preferable that apositioning protrusion is disposed at one of the upper side part fromthe base material opposing member of the processing head and the supportmeans, and a positioning recess for allowing the positioning protrusionto be vertically fitted thereto is disposed at the other of the upperside part from the base material opposing member of the processing headand the support means. Owing to this arrangement, the processing headcan surely be positioned at the support means.

The support means preferably includes an intake duct having an intakeport which is open downward and disposed in such a manner as to surroundthe processing head. Owing to this arrangement, the processed gas can beprevented from remaining in the space and discharged smoothly.Eventually, stain adhered to the base material opposing member can bereduced, and the frequency of maintenance can be reduced. Moreover,since the support means and the intake duct are composed of a commonmember, the number of parts can be reduced.

In the first feature, it is preferable that the processing head includesa member to be faced with the base material, the base material opposingmember includes a blowoff region where the first and second gas blowoffpassages are disposed and an expanding region expanded from the blowoffregion thereby to gain a ratio for forming a film, and the expandingregion is connected with an inert gas introduction means; and theexpanding region of the base material opposing member is composed of amaterial having such a degree of gas permeability that the inert gascoming from the gas introduction means is allowed to permeate toward abase material opposing surface and the degree of permeation and thus thedegree of oozing of the inert gas from the base material opposingsurface is such that the processing gas can be prevented from contactingthe base material opposing surface without disturbing a flow of theprocessing gas (see FIG. 34). Owing to this arrangement, a thin layer ofinert gas can be formed on the base material opposing surface,particularly on the expanding region, so that film can surely beprevented from adhering to the base material opposing surface. Inaddition, a film can sufficiently be formed while guiding the processinggas to the expanding region without disturbing the processing gas flowin the space between the processing head and the base material.

The gas permeating material is preferably a porous material. Owing tothis arrangement, the desired degree of permeation and thus oozing-outcan be obtained easily and reliably. Particularly, by composing the gaspermeating material from a porous material, an insulative property cansurely be obtained, too.

It is preferable that a groove for temporarily storing therein the inertgas coming from the gas introduction means is formed in an opposite sidesurface to the base material opposing surface in the expanding region ofthe base material opposing member in such a manner as to be recessedtoward the base material opposing surface. Owing to this arrangement,the base material opposing member in the expanding region can be reducedin thickness, and an inert gas film can surely be formed on the basematerial opposing surface, thereby a film can be prevented from beingadhered to this surface more reliably.

It is preferable that the base material opposing member has a shortdirection and a longitudinal direction, each of the regions extends inthe longitudinal direction, the expanding region is provided at bothsides in the short direction with the blowoff region sandwichedtherebetween, and the groove is formed in each expanding direction insuch a manner as to extend in the longitudinal direction. Owing to thisarrangement, a film can efficiently be formed over a wide range of areaat a time, and a film can surely be prevented from adhering to the twoexpanding regions.

It is preferable that the base material opposing member is entirelyintegrally formed from a gas permeating material, and a gas permeationprohibiting member for prohibiting gas permeation is disposed at aninner side surface facing with the blowoff region of the groove. Owingto this arrangement, the processing gas flow can surely be preventedfrom being disturbed or diluted in the blowoff region by inert gas, andtherefore, a high quality film formation can be enjoyed.

It is preferable that the groove is provided at an intermediate partthereof in a direction of the depth with a partition, the partition hasa sufficiently higher gas permeability than the gas permeating material,and the groove is partitioned into an upper-stage groove part continuouswith the inert gas introduction means and a lower-stage groove part nearthe base material opposing surface through the partition. Owing to thisarrangement, the inert gas can be uniformized within the groove. Thepartition is preferably composed of a porous plate which is more roughenough in mesh than the gas permeating material. Moreover, the gaspermeation prohibiting member is preferably disposed only at the innerside surface directing the blowoff region of the upper-stage groovepart. The lower-stage groove part is preferably larger in capacity thanthe upper-stage groove part. By disposing the gas permeation prohibitingmember only at the upper-stage groove part, the lower-stage groove canbe made larger in capacity than the upper-stage groove part.

In the first feature, it is preferable that a downstream end of thefirst flow passage is crossed with a downstream end of the second flowpassage, and the crossing part serves as a common blowoff port of thefirst and second gases (see FIG. 37). Owing to this arrangement, a filmcan be prevented from adhering to the opposing surfaces of therespective electrodes. Moreover, the first gas and the plasmatizedsecond gas can be mixed with each other simultaneously with the blowoff,and a sufficient film forming reaction can be obtained without waitingfor dispersion of the gases and before the active species are not lostin activity. Thus, the film forming efficiency can be enhanced.

In this mixing simultaneous blowoff construction, the first and secondflow passages are preferably crossed with each other at an acute angle.Owing to this arrangement, the first and second gases can be blownagainst the base material while being mixed such that the first andsecond gases form a single flow.

In the mixing simultaneous blowoff construction, it is preferable thatthe processing head includes a surface where the blowoff port is openand which is to be faced with the base material, one of the first andsecond flow passages is orthogonal to the base material opposingsurface, and the other is slantwise to the base material opposingsurface and crossed with the one flow passage at an acute angle. Owingto this arrangement, by blowing off one of the gases against the basematerial from right in front thereof and diagonally converging the othergas to the first-mentioned gas, a single gas flow can be obtained.

In the mixing simultaneous blowoff construction, it is preferable thatthe first and second flow passages are arranged such that the secondflow passage is disposed in such a manner as to sandwich or surround thefirst flow passage with the second flow passage disposed therebetween,and the second flow passage is approached to the first flow passagetoward the downstream end and crossed with each other at the blowoffport. Owing to this arrangement, the second gas can be converged to theopposite sides or around the first gas. One example, in which “thesecond flow passages sandwich the first flow passage therebetween”includes an arrangement in which two second flow passages are arrangedon the opposite sides of the first flow passage. Similarly, one example,in which “the second flow passages surround the first flow passage”includes an arrangement in which the second flow passages areconcentrically arranged with the first flow passage disposedtherebetween, so that the second flow passages will approach the firstflow passage. The concentric second flow passages may have an annularconfiguration in section enabling to surround the first flow passage,and are gradually reduced in diameter toward the downstream. In thealternative, the concentric second flow passages may be constructed suchthat they are composed of a plurality of branch passages spacedlyarranged in the peripheral direction of the first flow passage in such amanner as to surround the first flow passage, and those branch passagesgradually approach the first flow passage toward the downstream. Thefirst and second flow passages may be in reversed relation. That is, itis also accepted that the first flow passages are arranged such thatthey sandwich or surround the second flow passage disposed therebetween,and the first flow passages gradually approach the second flow passagetoward the downstream side and finally crossed with each other at theblowoff port.

In the mixing simultaneous blowoff construction, it is preferable thatthe processing head is provided with two each of the electric fieldimpressing electrodes and the ground electrodes, the two electric fieldimpressing electrodes are disposed at the first flow passage in such amanner as to be faced with each other, one each of the electric fieldimpressing electrodes is faced with one each of the ground electrodeswith the second flow passage formed therebetween, the two second flowpassages are arranged in such a manner as to be approached to the firstflow passage toward the downstream end with one of the first flowpassages sandwiched therebetween, and three of those passages arecrossed with one another at the blowoff port. Owing to this arrangement,the plasmatized second gas can be converged to the first gas from bothside of the first gas.

Moreover, it is preferable that the processing head includes a surfacewhere the blowoff port is open and which is to be faced with the basematerial; the first flow passage between the two electric fieldimpressing electrodes is orthogonal to the base material opposingsurface, each of the two electric field impressing electrodes includes afirst surface located on the reverse side to the side which is facedwith the first flow passage and slantwise with respect to the basematerial opposing surface; and each of the two ground electrodesincludes a second surface which is faced in parallel with the firstsurface of the corresponding electric field impressing electrode andforming the second flow passage therebetween. Owing to this arrangement,the respective electric field impressing electrodes can be arranged onthe reverse side to the base material with the ground electrodesandwiched therebetween, arc discharge to the base material from theelectric field impressing electrodes can be prevented from occurring,and a favorable film forming processing can surely be conducted.Moreover, by blowing off the first gas against the base material fromright in front thereof and diagonally converging the plasmatized secondgas to the opposite sides of the first gas, a single gas flow can beobtained.

In the construction having two second flow passages arranged on oppositesides of the first flow passage, the two second flow passages arepreferably symmetrical with each other with the first flow passagesandwiched therebetween. Owing to this arrangement, the plasmatizedsecond gas can be uniformly converged to the first gas from the oppositesides of the first gas.

The ground electrode preferably includes the base material opposingsurface. Owing to this arrangement, arc discharge to the base materialfrom the respective electric field impressing electrodes can more surelybe prevented from occurring.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view of a plasma film forming apparatus accordingto a first embodiment of the present invention.

FIG. 2 is a front sectional view of a gas uniformizing part of aprocessing head of the plasma film forming apparatus.

FIG. 3 is a front sectional view of a nozzle part of the processinghead.

FIG. 4 is a side sectional view taken along the longitudinal directionof the gas uniformizing part.

FIG. 5 is a side sectional view of the nozzle part taken on line V-V ofFIG. 3.

FIG. 6 is a plan sectional view of a left side part of the nozzle parttaken on line VI-VI of FIG. 3.

FIG. 7 is a bottom view of the processing head.

FIG. 8 is an enlarged view of a gas blowoff part of the processing head.

FIG. 9 is a front sectional view showing a manner for separating a headmain body of the processing head and a nozzle tip composing member atthe time of maintenance.

FIG. 10 is a detailed view of a power feed pin of the nozzle part.

FIG. 11 is a front sectional view of a nozzle part of a processingnozzle in a plasma film forming apparatus according to a secondembodiment of the present invention.

FIG. 12 is a bottom view of the processing head of the secondembodiment.

FIG. 13 is a front sectional view of a processing head in a plasma filmforming apparatus according to a third embodiment of the presentinvention.

FIG. 14 is a sectional view showing a modified embodiment of the thirdembodiment.

FIG. 15 is a front sectional view of a nozzle part of a processing headin a plasma film forming apparatus according to a fourth embodiment ofthe present invention.

FIG. 16 is a side sectional view of the nozzle part taken on lineXVI-XVI of FIG. 15.

FIG. 17 is a plan sectional view of the nozzle part taken on lineXVII-XVII of FIG. 15.

FIG. 18 is a bottom part of a processing head of the fourth embodiment.

FIG. 19 is an exploded perspective view of an electric field impressingelectrode of the fourth embodiment.

FIG. 20 is an enlarged view of a gas blowoff part of the fourthembodiment.

FIG. 21 is an enlarged view of a gas blowoff part showing a modifiedembodiment of a ground electrode structure of the fourth embodiment.

FIG. 22 is a schematic construction view of a plasma film formingapparatus according to a fifth embodiment of the present invention.

FIG. 23 is a schematic structure view of a plasma film forming apparatusaccording to a sixth embodiment of the present invention.

FIG. 24 is a sectional view showing a modified embodiment of aconnection structure of an electric field impressing electrode and anelectricity feed line.

FIG. 25 is an exploded perspective view showing a modified embodiment ofan induction case of an electrode.

FIG. 26 is a front sectional view showing another modified embodiment ofan induction case.

FIG. 27 is an exploded perspective view of the induction case of FIG.26.

FIG. 28 is a perspective view showing a modified embodiment of anelectrode structure with an induction case.

FIG. 29 is a perspective view showing another modified embodiment of anelectrode structure of an induction case.

FIG. 30 is a front sectional view of an electrode structure having a gasuniformizing part integrated induction case.

FIG. 31 is a side view of a gas uniformizing part integrated inductioncase taken on line XXXI-XXXI of FIG. 30.

FIG. 32 is a front sectional view of an electrode structure having aninduction case with a tree-type passage.

FIG. 33 is a side view of the induction case with a tree-type passagetaken on line XXXIII-XXXIII of FIG. 32.

FIG. 34 is a view showing a schematic construction of a normal pressureplasma film forming apparatus according to a seventh embodiment of thepresent invention and a front section of a processing head of theapparatus.

FIG. 35 is a plan view of a lower plate of the processing head taken online XXXV-XXXV of FIG. 34.

FIG. 36 is a side sectional view of a nozzle part of the processing headtaken on line XXXVI-XXXVI of FIG. 35.

FIG. 37 is a view a schematic construction of a normal pressure plasmafilm forming apparatus according to an eighth embodiment of the presentinvention and a front section of a processing head of the apparatus.

FIG. 38 is an enlarged sectional view of a nozzle of the processing headof FIG. 37.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described hereinafter withreference to the drawings.

FIG. 1 shows a normal pressure plasma film forming apparatus M1according to a first embodiment of the present invention. The normalpressure plasma film forming apparatus M1 comprises a frame (supportmeans) including a housing 10, a processing head 3 supported on thehousing 10 of the frame, two kinds of processing gas sources 1, 2connected to the processing head 3, and a power source 4. Beneath theprocessing head 3, a plate-like base material W (object to be processed)having a large area is transferred in the left and right direction bytransfer means (not shown) It is, of course, accepted that the basematerial W is fixed and the processing head 3 is moved. In the normalpressure plasma film forming apparatus M1, a film A (FIG. 8) such as,for example, amorphous silicon (a-Si) and silicon nitride is formed onan upper surface of this base material W.

Of the two kinds of processing gas sources, a raw material gas source 1(first gas source) stores therein a raw material gas (first gas, forexample, silane) which forms a film A such as the above-mentionedamorphous silicon. An excitable gas source 2 (second gas source) storestherein an excitable gas (second gas, for example, hydrogen andnitrogen). The excitable gas, when excited by plasma, causes the rawmaterial such as the silane to be reacted to form the film A such asamorphous silicon or the like. On the other hand, the excitable gas doesnot include a component (film raw material) which is not formed into afilm alone even when excited by plasma. Each gas may be stored in aliquid phase and evaporated by an evaporator.

The raw material gas and the excitable gas is generally referred to asthe “processing gas”.

A pulse power source 4 (electric field impressing means) outputs a pulsevoltage to the electrode 51. This pulse voltage preferably has a pulserise time and/or pulse fall time of 10 μs or less, 200 μs or less ofpulse duration, 1 to 1000 kV/cm of electric field strength, and 0.5 kHzor more of frequency.

The housing 10 for receiving and supporting the processing head 3includes a left and a right wall 11 having, for example, a semi-circularconfiguration in side view and a front and a rear low wall forconnecting the lower parts of the walls 11. The housing 10 has a squareconfiguration in plane view. The housing 10 as a support means of theprocessing head 3 also serves as an intake duct. That is, as shown inFIGS. 3 and 6, the front, rear, left and right walls 11, 12 are ofhollow structure. The lower end parts of those hollow parts 10 b areopen to the lower end faces of the walls 11, 12, thereby forming anintake port 10 a surrounding the outer periphery of the lower end of theprocessing head 3. As shown in FIG. 1, openings 11 b continuous with thehollow parts 10 b are disposed at the upper end parts of the left andright walls 11. A gas exhaust passage 13 extends from each upper endopening 11 b. After converged, those gas exhaust passages 13 areconnected to a pump 14 (gas exhaust means).

The processing head 3 has a generally rectangular parallelepipedconfiguration which is long is the back and forth direction. Theprocessing head 3 is received in and supported by the housing 10 suchthat the processing head 3 is surrounded with the front, rear, left andright walls 11, 12. The support structure of the processing head 3 willnow be described.

As shown in FIGS. 3 and 7, the housing 10 is provided at the lower endedges of the inner wall surfaces of the left and right walls 11 eachwith an inner flange 11 d. A lower frame 24 of the processing head 3 isplaced on the inner flanges 11 d such that the left and right parts ofthe lower frame 24 are hooked on the inner flanges lid. As shown inFIGS. 5 and 7, the housing 10 is also provided at the front and rearwalls 12 each with an inner flange 12 d. The front and rear parts of thelower frame 24 are placed on the inner flanges 12 d, respectively.

As shown in FIG. 1, the front and rear walls 12 are formed at the upperend faces each with a positioning recess 12 b (head support part) whichis recessed in a form of a reversed triangle. On the other hand, a sideframe 23 of the processing head 3 is provided with a positioningprotrusion 23 a which has a reversed triangular configuration. Thepositioning protrusion 23 a is fitted to the positioning recess 12 b.Owing to this arrangement, the processing head 3 is positioned to andsupported by the housing 10.

It is also accepted that the positioning recess is provided at theprocessing head 3 and the positioning protrusion is provided at thehousing (support means) 10.

As shown in FIG. 1, the processing head 3 is comprised of a gasuniformizing part 30 and a nozzle part 20 on which the gas uniformizingpart 30 is superimposed. Gas is introduced to the gas uniformizing part30 on the upper side from the gas sources 1, 2. The gas uniformizingpart 30 uniformizes this gas in the longitudinal direction of theprocessing head 3 and supplies it to the nozzle part 20 which is locatedbeneath.

More specifically, as shown in FIGS. 2 and 4, the gas uniformizing part30 is constituted by laminating a plurality of copper-made plates 31through 38 extending forward and backward. Those plates 31 through 38,i.e., gas uniformizing part 30 includes three gas flowing regions 30B,30A, 30B which are imaginarily dividingly set leftward and rightward.

As shown in FIG. 1, the second-stage plate 32 is provided at a front endpart (one end part) thereof with three gas plugs 32P which are arranged,in side-by-side relation, leftward and rightward corresponding to theregions 30B, 30A, 30B. The gas plug 32P in the central raw material gasflowing region 30A is connected with the raw material gas source 1through a raw material gas tube 1 a. The gas plugs 32P in the left andright excitable gas flowing regions 30B, 30B are connected with theexcitable gas source 2 through an excitable gas tube 2 a. The excitablegas tube 2 a extends in the form of a single tube from the excitable gassource 2 and then branched into two tubes so as to be connected with thegas plugs 32P in the respective regions 30B, 30B.

As shown in FIG. 2, the plates 32 through 38 at the second stage throughthe lowermost stage are provided with gas uniformizing passages 30Xwhich are each formed in the regions 30B, 30A, 30B, respectively. Thosegas uniformizing passages 30X are of mutually same structure.

As shown in FIGS. 2 and 4, as the gas uniformizing passages 30 x in therespective regions 30B, 30A, 30B, the second-stage plate 32 is formed ata front end part thereof with an inlet port 32 b which is connected withthe gas plug 32P. The second-stage plate 32 is further formed with adeep reversely recessed groove 32 a which extends to a central part inthe back and forth direction of the plate 32 and open to a lower surfacethereof.

The third-stage plate 33 is formed at a central part in the back andforth direction thereof with a pair of left and right communicationholes 33 a, 33 b which are connected to the reversely recessed groove 32a.

The fourth-stage plate 34 is formed with a line groove 34 b which isconnected to the communication hole 33 a and extends backward, acommunication hole 34 c which extends to from a terminal end (rear end)of this line groove 34 a to a lower surface thereof, and a line groove34 b which is continuous with the communication hole 33 b and extendsforward, and a communication hole 34 d extending from a terminal end(forward end) of this line groove 34 b to a lower surface thereof.

The fifth-stage plate 35 is formed with a line groove 35 a which iscontinuous with the communication hole 34 c and extends generally overthe entire length in the back and forth longitudinal direction, a linegroove 35 b which is continuous with the communication hole 34 d andextends generally over the entire length in the back and forthlongitudinal direction, and a plurality of small holes (pressure lossforming passages) 35 c, 35 d which extend from the respective linegrooves 35 a, 35 b to the lower surfaces and which are arranged at equalpitches in the back and forth direction.

The sixth-stage plate 36 is formed with a wide line groove (expansionchamber) 36 a which is continuous with the small holes 35 c, 35 d andextends generally over the entire length in the back and forthlongitudinal direction, and a plurality of small holes (pressure lossforming passages) 36 b which extend from the line groove 36 a to thelower surface and which are arranged zigzag in two rows at equal pitchesin the back and forth direction.

The seventh-stage plate 37 is formed with a wide line groove (expansionchamber) 37 a which is continuous with the small holes 36 b and whichextend generally over the entire length in the back and forthlongitudinal direction, and a plurality of small holes (pressure lossforming passages) 37 b which extend from this line groove 37 a to thelower surface and which are arranged zigzag in two rows at equal pitchesin the back and forth direction.

The lowermost-stage plate 38 is formed with a wide through-hole(expansion chamber) 38 a which is continuous with the small holes 37 band which extend generally over the entire length in the back and forthlongitudinal direction. This through-hole 38 a constitutes a downstreamend of the gas uniformizing passage 30 x. As later described, thethrough-hole 38 a is in communication with guide passages 27 b, 27 a, 27b of an insulative plate 27.

The uppermost-stage plate 31 receives therein a thin and elongate plateheater 31H which is adapted to heat the gas uniformizing passage 30 xand which extends in the back and forth direction. The second throughlowermost-stage plates 32 through 38 are formed with a slit 30 s alongthe borders of the regions 30B, 30A, 30B. Owing to this arrangement, theregions 30B, 30A, 30A are individually thermally isolated (broken off)from one another.

In FIGS. 1 and 2, reference numeral 39S denotes a bolt for jointing theuppermost-stage plate 31 with the second-stage plate 32, and referencenumeral 39L denotes a bolt for jointing the second throughlowermost-stage plates 32 through 38 altogether.

Next, the nozzle part 20 of the processing head 3 will be described. Asshown in FIG. 3, the nozzle part 20 comprises a nozzle body 21, anelectrode unit 50 received in the nozzle body 21, an insulative plate 27for covering this unit 50, base material opposing members 24, 25disposed at a lower side of the unit 50. As shown in FIG. 6, the nozzlebody 21 includes metal-made left and right side frames 22 extending longin the back and forth direction, and insulative resin-made front andrear side frames 23 which are disposed between the front and rear endparts of the side frames 22, respectively. The nozzle body 21 has abox-like configuration which is long in the back and forth direction.The side frame 22 is jointed to the lowermost-stage plate 38 of the gasuniformizing part 30 by a bolt 26A (FIG. 30).

As shown in FIGS. 3 and 7, the lower frame 24 constituting one elementof the base material opposing member is made of metal such as stainlessand aluminum, and it has a rectangular configuration extending in theback and forth direction. As mentioned above, the lower frame 24 issupported in such a manner as to be hooked on inner flanges 11 d, 12 dof the housing 10. The side frames 22 are placed on the lower arm 24.Although the lower arm 24 and the side frames 22 are merely contactedand not jointed with each other, they may be jointed through an easyremovably attaching mechanism such as a bolt and a hook.

As shown in FIG. 3, a step 24 a is formed on an inner peripheral edge ofthe lower frame 24. A peripheral edge part of the rectangular lowerplate 25 constituting a main element of the base material opposingmember is placed and supported on this step 24 a in such a manner as tobe hooked thereon. The lower plate 25 is composed of a ceramic(dielectric member or insulative member) such as, for example, alumina.An electrode receiving recess 25 c is formed in an upper surface of thelower plate 25. The electrode unit 50 is fitted to this receiving recess25 c.

As shown in FIGS. 3 and 5, a more shallow recess 25 d is disposed at thereceiving recess 25 c formed in the upper surface of the lower plate 25.The recess 25 d is wide, and it extends in the back and forth direction.As shown in FIG. 3, a blowoff passage (blowoff aperture) 25 a extendingfrom the recess 25 d to the lower surface is formed in a central part inthe left and right direction of the lower plate 25. As shown in FIG. 7,the blowoff passage 25 a has a slit-like configuration, and it extendsin the back and forth direction.

As shown in FIG. 3, the insulative plate 27 composed of a ceramic(insulative member) is vertically sandwiched between the lowermost-stageplate 38 of the gas uniformizing part 30 and the electrode unit 50. Theinsulative plate 27 is formed with three gas guide passages 27 b, 27 a,27 b which extend generally over the entire length in the longitudinaldirection and separately arranged in the left and right direction. Thecentral raw gas guide passage 27 a vertically pierces through theinsulative plate 27. The right side excitable gas guide passage 27 b isslanted leftward from the upper surface of the insulative plate 27toward downward direction and it finally reaches a lower surface of theplate 27. The left side excitable gas guide passage 27 b is slantedrightward from the upper surface of the insulative plate 27 towarddownward direction, and it finally reaches the lower surface of theplate 27.

As shown in FIGS. 3 and 6, the electrode unit 50 comprises an electrodegroup consisting of four (a plurality of) electrodes 51, 52, a pair ofleft and right side plates 53, and a pair of front and rear end plates54. Each of the electrodes 51, 52 is constituted by providing an arcpreventive solid dielectric layer 59 to the surface of a main body 56made of metal such as aluminum and stainless steel. The metal main body56 has a vertically long square configuration in section and extendslong in the back and forth direction. The solid dielectric layer 59 iscomposed of a dielectric member such as ceramic and coated in the formof film on a surface on the side of a flow passage 50 b, as laterdescribed, and upper and lower surfaces of the metal main body 56 bythermally sprayed coating or the like. Instead of thermally sprayedcoating, a resin sheet such as poly-tetrafluoro-ethylene may be adheredto the metal main body 56.

The four electrodes 51, 52 are arranged in mutually parallel relation inthe left and right direction.

In the electrode group, the two electrodes 51 on the middle side areelectric field impressing electrodes (first electrodes), and the twoelectrodes 52 on both left and right ends (both ends in the arrangingdirection) are ground electrodes (second electrodes). Accordingly, theelectrode group is constituted by arranging the ground electrode 52, theelectric field impressing electrode 51, the electric field impressingelectrode 51 and the ground electrode 52 in this order in the left andright direction.

Each of the electrodes 51, 52 may be formed therein with a temperaturecontrolling passage for allowing a temperature controlling cooling waterto pass therethrough.

The side plates 53 of the electrode unit 50 are each made of aninsulative resin. The side plates 53 are placed along rear surfaces(reversed side surfaces of the opposing side with respect to theelectrode 51) of the left and right electrodes 52 and sandwich theelectrode group from the left and right sides. A bolt 26 screwed inthrough the side frame 22 is abutted with a rear surface of the sideplate 53. Owing to this arrangement, the electrode unit 50 is correctlypositioned and retained within the nozzle body 21.

The end plates 54 of the electrode unit 50 are each made of aninsulative resin. The end plates 54 are applied to both end faces in thelongitudinal direction of the four electrodes 51, 52 and sandwich theelectrode group from the front and rear side.

A feeding/grounding structure of the electrodes 51, 52 will bedescribed. As shown in FIG. 6, a feed pin 40 is embedded in, forexample, a front end part (one end part in the longitudinal direction)of each of the two electric field impressing electrodes on the middleside, and a ground pin 40A having the same construction as the feed pin40 is embedded in a rear end part (the other end part in thelongitudinal direction) of each of the two electrodes 52 on both theleft and right sides.

As shown in FIG. 10, the feed pin 40 for the electric field impressingelectrode 51 comprises a shaft-like pin main body 41 having a shaft hole41 a which is open to a forward end face, a barrel body 42 received inthe shaft hole 41 a, and a core member 43 slideably received in thisbarrel body 42. The pin main body 41, the barrel body 42 and the coremember 43 are composed of a conductive metal such as stainless steel andthey are electrically conducted by being abutted with one another attheir inner and outer peripheral surfaces.

A forward end part of the pin main body 41 is withdrawably pushed into apin hole 56 a formed in a front end face of the electric fieldimpressing electrode 51. Owing to this arrangement, the pin main body 41and the electrode 51 are electrically conducted with each other. Acoiled spring 44 (biasing means) is received in the barrel body 42. Bythis coiled spring 44, the core member 43 is biased in the forward enddirection, i.e., in the direction to be pushed out of the shaft hole 41a. Owing to this arrangement, the forward end part of the core member 43is pressed hard against the innermost end face of the pin hole 56 a. Asa result, the electrically conducting state between the feed pin 40 andthe electrode main body 56 is surely maintained.

Barrel-like pin holders 45A, 45B, which are each made of an insulativemember are mounted on a basal end part (head part) of the pin main body41. The basal end part of the holder-mounted pin main body 41 projectsfrom the end plate 54 and is disposed between the front side end plate54 and the side frame 23. As shown in FIG. 5, a power feed line 4 aextends from the basal end part of this main body 41 and is connected tothe pulse power source 4.

The ground pin 40A for the ground electrode 52 has the same constructionas the feed pin 40. As shown in FIG. 6, the head part of the ground pin40A projects from the rear side end plate 54. A ground line 4 b isconnected to the head part of the ground pin 40A. The ground line 4 b isallowed to pass between the upper surface of the rear-side side frame 23and the insulative plate 27 and pulled outside of the processing head 3so as to be grounded.

As shown in FIGS. 3 and 6, flow passages 50 a, 50 b for the processinggas, i.e., the raw material gas or excitable gas are formed between theadjacent electrodes 51, 52.

More specifically, between the middle side electrodes 51, 51 having thesame polarities, the flow passage 50 a for the raw material gas isformed. Between both the left and right side electrodes 52, 51 havingdifferent polarities, one each of the flow passages 50 b (plasmadischarge space) for the excitable gas is formed. Accordingly, theexcitable gas flow passage 50 b, the raw material gas flow passage 50 a,and the excitable gas flow passage 50 b are arranged in this order fromthe left.

The electrode unit 50 is provided at the front and rear end plates 54with three plate piece-like spacers 55 which are each made of aninsulative resin. Those plate piece-like spacers 55 are pushed inbetween the adjacent electrodes 51, 52, thereby establishing the widthof each of the flow passages 50 b, 50 a, 50 b.

As shown in FIG. 3, an upper end part (upstream end) of the central flowpassage 50 a is straightly continuous with the gas uniformizing passage30 x in the central region 30A of the gas uniformizing part 30 throughthe central guide passage 27 a of the insulative plate 27, and thus withthe raw material gas source 1 through the tube 1 a.

The surface for forming the flow passage 50 a of each electric fieldimpressing electrode 51 is indented at an upper side thereof andprojected at a lower side thereof. A step is formed at an intermediatepart of the flow passage forming surface. Owing to this arrangement, theflow passage 50 a is enlarged in width at the upper side and reduced inwidth at the lower side.

Upper end parts (upstream ends) of the flow passages 50 b, 50 b on theleft and right sides are continuous with the gas uniformizing passages30 x, 30 x in the left and right regions 30B, 30B of the gasuniformizing part 30 through the left and right guide passages 27 b, 27b of the insulative plate 27, and thus, with the excitable gas source 2through the tube 2 a.

Each ground electrode 52 is placed on an upper surface of the electrodereceiving recess 25 c of the lower plate 25. On the other hand, as shownin FIGS. 3 and 5, the respective electric field impressing electrodes 51are spacedly arranged at an upper part of the recess 25 d of the lowerplate 25. Owing to this arrangement, a gap 20 b is formed between thelower surface of each electric field impressing electrode 51 and thelower plate 25.

As shown in FIG. 3, those left and right gaps 20 b each serve as acommunication passage for communicating the flow passage 50 b betweenthe electrodes having different polarities with the flow passage 50 abetween the electrodes having the same polarities. That is, a left endpart (upstream end) of the left side communication passage 20 b iscontinuous with the flow passage 50 b between the electrodes havingdifferent polarities, and a right end part (downstream end side) iscrossed with the lower end part (downstream end) of the electrodepassage 50 a between the electrodes having the same polarities. Theright end part (upstream end) of the right side communication passage 20b is continuous with the flow passage 50 b between the right sideelectrodes having different polarities, and the left end part(downstream end) is crossed with the downstream end of the flow passage50 a between the electrodes having the same polarities.

The flow passage 50 a between the electrodes having the same polaritiesconstitutes the “first flow passage”, and the flow passage 50 a betweenthe electrodes having different polarities and the communication passage20 b constitutes the “second flow passage”.

The electrodes 51, 51 having the same polarities constitute the “firstflow passage forming means”. The electrodes 51, 52 having differentpolarities, and the electrode 51 and the lower plate 25 constitute the“second flow passage forming means”.

The left and right communication passages 20 b are horizontal andorthogonal to the vertical first flow passage 50 a. The left and rightsecond flow passages 50 b, 20 b are symmetrical with each other withrespect to the central first flow passage 20 a sandwiched therebetween.

As shown in FIG. 8 on an enlarged basis, the blowoff passage 25 a of thelower plate 25 is continuous with a crossing part (converging part)among the three flow passages 20 b, 50 a, 20 b. This blowoff passage 25a serves as a common blowoff passage of the raw material gas and theexcitable gas, and its downstream end (blowoff port) is open to a lowersurface of the lower plate 25. The blowoff passage 25 a is disposedright under the vertical flow passage 50 a.

Operation of the normal pressure plasma film forming apparatus M1 thusconstructed will now be described.

The Excitable gas (second gas) such as hydrogen coming from theexcitable gas source 2 is introduced, via the gas tube 2 a, into the gasuniformizing passages 30 x in the left and right regions 30B from twoleft and right plugs 32P of the processing head 3 and uniformized in theback and forth longitudinal direction by those passages 30 x. Theexcitable gas thus uniformized is introduced into the left and rightflow passages 50 b via the left and right guide passages 27 b,respectively.

On the other hand, the voltage coming from the pulse power source 4 isfed to the electric field impressing electrode 51, and a pulse electricfield is impressed between the electrodes 51, 52 having differentpolarities. By this, as shown in FIG. 8, Glow discharge is generated inthe left and right flow passages 50 b, and the excitable gas isplasmatized (excited and activated). The excitable gas thus plasmatizedis guided into the communication passage 20 b from the flow passage 50 band allowed to flow toward the crossing part 20 c. This excited gasitself does not contain any component which is adhered to and depositedon the surface of ceramic or the like by excitation. Accordingly, itnever happens that film is adhered to the opposing surfaces between theelectrodes 51, 52 having different polarities, the lower surface of theelectrode 51 and the upper surface (second flow passage forming surface)of the lower plate 25.

Simultaneously with the flowing of the excitable gas, the raw materialgas (first gas) such as silane gas coming from the raw material gassource 1 is introduced, via the gas tube 1 a, into the gas uniformizingpassage 30 x in the central region 30A from the central gas plug 32P ofthe processing head 3 and uniformized in the back and forth longitudinaldirection. Thereafter, the gas is introduced, via the central guidepassage 27 a, into the central flow passage 50 a between the electrodeshaving the same polarities. Although pulse voltage is fed to each of thetwo electric field impressing electrodes 51, no electric field isimpressed between those electrodes 51, 51 having the same polarities andtherefore, it never happens that plasma discharge occurs at the flowpassage 50 a. Thus, the raw material gas is allowed to pass as it iswithout being plasmatized. For this reason, a film is not adhered to theopposing surfaces (first flow passage forming surface) between theelectrodes 51 having the same polarities.

Since no film is attached to anywhere of the four electrodes,maintenance of the electrodes 51, 52 becomes easy. Moreover, loss of theraw material occurrable at the time of passage between the electrodescan be eliminated.

The raw material gas passing through the flow passage 50 a is reduced atthe lower side of the passage 50 a where the passage 50 a is narrow andtherefore, the pressure is increased.

After passing through the central flow passage 50 a, the raw materialgas flows to the crossing part 20 c between the left and rightcommunication passages 20 b. The excitable gas plasmatized in the leftand right flow passages 50 b also flows to the crossing part 20 cthrough the communication passage 20 b. By this, the raw material gas iscontacted with the plasmatized excitable gas (active species) so as totake place such reaction as decomposition and excitation, therebygenerating a radical reaction production p which is turned out to be afilm.

The excitable gas flow entering the crossing part 20 c from the left andright passages 20 b is pushed by the raw material gas flow and curveddownward. By this, the excitable gas mostly flows along the right sideedge surface and the left side edge surface of the blowoff passage 25 a,and the raw material gas mostly flows in such a manner as beingsandwiched between the left and right excitable gas flows and passesthrough the middle side of the blowoff passage 25 a. This makes itpossible for the reaction product p scarcely to contact the edge surfaceof the blowoff passage 25 a. Therefore, adhesion of a film to the edgesurface of the blowoff passage 25 a can be reduced, and the raw materialloss can further be reduced.

Then, the processing gas (excitable gas and raw material gas) is blownoff from the blowoff passage 25 a generally in a laminar flow state. Bythis, a desired film A can be formed by applying the reaction product pto the upper surface of a base material W placed immediately under theblowoff passage 25 a.

Since the gas is uniformized in the back and forth direction by the gasuniformizing part 30, the film A, which is uniform in the back and forthdirection, can be formed.

Thereafter, the processing gas flows in the two left and rightdirections through the space between the processing head 3 and the basematerial W in such a manner as to be away from the blowoff passage 25 a.At that time, the excitable gas is mostly one-sided toward theprocessing head 3 side, and the raw material gas is mostly one-sidedtoward the base material W side located thereunder. By this, thereaction product p can be maintained in a state hardly contacting thelower surfaces of the lower plate 25 and the lower frame 24. As aresult, film adhesion to those members 25, 24 can be reduced, andfrequency of film removal can be reduced.

The processed gas is taken into the housing 10 through the intake port10 a and then discharged by actuation of a vacuum pump 14. Bycontrolling the intake pressure of this vacuum pump 14, etc., theexcitable gas and the raw material gas can be maintained in thegenerally laminar flow state, and film adhesion to the processing head 3can more surely be prevented from occurring.

For example, even if a film should be formed on the base materialopposing member (lower frame 24 and lower plate 25), by pulling outprocessing head 3 and taking it out of the housing 10 as shown in FIG.9, only the base material opposing members 24, 25 would left remained inthe state hooked on the inner flanges 11 d, 12 d of the housing 10. Bythis, the base material opposing members 24, 25 can be separated fromthe processing heads 3 very easily. Thereafter, only the base materialopposing members 24, 25 are subjected to cleaning process by beingdipped in a chemical liquid such as, for example, strong acid, so that afilm can be removed. Since the entire processing head 3 is no morerequired to be subjected to cleaning process, maintenance can besimplified. On the other hand, by preparing spare parts of the basematerial opposing members 24, 25 and attaching them to the apparatus M1,the film forming processing can be kept continued even during thecleaning process.

According to the normal pressure plasma film forming apparatus M1, sincethe power feed line 4 a is pulled out of one end part of the processinghead and a ground line 4 b is pulled out of the other end part (FIGS. 5and 7), those lines 4 a, 4 b can be prevented from beingshort-circuited.

Moreover, the power feed/ground lines 4 a, 4 b and the electrode mainbody 56 can be electrically connected through the power feed/ground pins40, 40A surely and easily. Since the power feed/ground pins 40, 40A caneasily be removed, they can not be any disturbance at the time ofmaintenance.

Moreover, the two ground electrodes 52 are arranged on the left andright outer sides with the two electric field impressing electrodes 51sandwiched therebetween, electric field can be prevented from leakingoutside and the entire processing head 3 can easily be grounded, too.

Other embodiments of the present invention will be described next. Inthe embodiments to be described hereinafter, the same construction as inthe above-mentioned embodiment is denoted by same reference numeral inFigures so that description thereof can be simplified.

FIGS. 11 and 12 show a second embodiment of the present invention. Inthe second embodiment, the blowoff ports for the first and second gasesare separately formed.

More specifically, as shown in FIG. 12, a lower plate 25 is formed withthree slit-like individual blowoff passages 25 b, 25 a, 25 b whichextend in the back and forth direction and which are arranged inparallel at equal intervals in the left and right direction.

As shown in FIG. 11, the left side blowoff passage 25 b is continuousstraight with a lower part of a flow passage 50 b between the left sideelectrodes 52, 51 having different polarities. The central blowoffpassage 25 a is continuous straight with a lower part of a flow passage50 a between the central electrodes 51, 51 having the same polarities.The right side blowoff passage 25 b is continuous straight with a lowerpart of the flow passage 50 b between the right side electrodes 51, 52having different polarities. The lower end parts of those three blowoffpassages 25 b, 25 a, 25 b are open to a lower surface of the lower plate25. The lower end opening of the central blowoff passage 25 aconstitutes a blowoff port for a raw material gas (first gas), and thelower end openings of the left and right blowoff passages 25 bconstitute blowoff ports for an excitable gas (second gas).

The lower plate 25 is not provided at an electrode receiving recess 25 cwith the recess 25 d of the first embodiment, and an electric fieldimpressing electrode 51 is abutted with the upper part of the receivingrecess 25 c. Accordingly, the communication passage 20 b of the firstembodiment is not formed.

The raw material gas guided into the central flow passage 50 a is blownoff directly through the blowoff passage 25 a, and thereafter, allowedto flow separately in the two left and right directions between thelower plate 25 and a base material W. On the other hand, the excitablegas guided into the left and right flow passages 50 b is plasmatized(excited and activated) by the electric field between the electrodes 51,52 having different polarities, and thereafter, blown off through theleft and right blowoff passages 25 b. The raw material gas flowing onthe base material W contacts the excitable gas thus blown off. As aresult, reaction is taken place. By this, a film A is formed on the basematerial W. Thereafter, the excitable gas and the raw material gas flowtoward an intake port 10 a in their vertically overlapped generallylaminar flow states and then, they are discharged.

FIG. 13 shows a third embodiment of the present invention.

In the third embodiment, an electrode group consisting of eight (aplurality of) planar electrodes 51, 52 is disposed within a metalconductor-made nozzle body 20B of a processing head 3. Those electrodesare in mutually parallel relation and arranged at equal intervals in theorder of the ground electrode 52, the electric field impressingelectrode 51, the ground electrode 52, the ground electrode 52, theelectric field impressing electrode 51, the electric field impressingelectrode 51 and the ground electrode 52 from left. Owing to thisarrangement, the second flow passages (plasma discharge space) 50 bbetween the electrodes having different polarities and the first flowpassages 50 a between the electrodes having the same polarities arealternately arranged. Each first flow passage 50 a allows the rawmaterial gas (first gas) from a raw material gas source (not shown) topass therethrough, and each second flow passage 50 b allows theexcitable gas (second gas) from an excitable gas source (not shown) topass therethrough.

The ground electrodes 52 located at the opposite end parts in thearranging direction of the electrode group are abutted at their rearsurfaces along a nozzle body 20B and electrically conducted with thisnozzle body 20B. Although not shown specifically, the central side twoground electrodes 52 are abutted at opposite end parts in thelongitudinal direction (orthogonal direction to the paper surface ofFIG. 13) with the nozzle body 20B and electrically conducted with thisnozzle body 20B. The nozzle body 20B is grounded through the ground line4 b. Owing to this arrangement, the entire processing head 3 can begrounded and at the same time, the ground electrode 52 can be grounded.

In the third embodiment, the ground electrodes 52 located at theopposite outer sides may be integrally formed with the nozzle body 20B.That is, the nozzle body 20B may serve also as the ground electrodes 52located at the opposite outer sides.

In the third embodiment, the number of the electrodes in the electrodegroup is not limited to eight but it may be three, five to seven, ornine or more. Those electrodes are arranged such that differentpolarities space (second flow passage) for allowing the second gas topass therethrough and the same polarities space (first flow passage) forallowing the first gas to pass therethrough are alternately formed. Thatis, those electrodes are arranged in the order of the second electrode,the first electrode, the first electrode, the second electrode, thesecond electrode, the first electrode, the first electrode, the secondelectrode, the second electrode, the first electrode, the firstelectrode, the second electrode and so on. The second electrode as theground electrode is preferably arranged at the outermost side. In casethe number of the electrodes is even in total, the number of the firstelectrodes is equal to the number of the second electrodes. In case thenumber of the electrodes is odd in total, the number of the secondelectrodes becomes larger than the number of the first electrodes byone. It is accepted that the electrodes having the same polarities(preferably, ground electrodes) are arranged at the outermost side andat an inner location next to the outermost side, and the first gas ispassed through the opposing space at the outermost side. It is alsoaccepted that a plurality of first and second electrodes, which are solong as almost equal to the entire length of a base material having alarge area, are arranged over the entire width of the base material inthe above-mentioned order so that the entire base material can be formedwith a film at a time.

Moreover, the first and second flow passages may be alternately arrangedone by one. It is also accepted that a plurality of at least one of thefirst and second flow passages are arranged adjacent to each other, andgroups of such adjacent flow passages and the other flow passages arealternately arranged in parallel.

FIG. 14 shows a modified embodiment of such an alternate arrangementconstruction. The processing head 3 of this modified embodiment, a groupof electrodes are arranged in the order of the second electrode 52, thefirst electrode 51, the second electrode 52, the second electrode 52,the first electrode 51 and the second electrode 52. Owing to thisarrangement, one of such first flow passages 50 a is arranged at thecenter and two of such second flow passages 50 b are arranged on theopposite left and right sides thereof. That is, two (a plurality of)second flow passages 50 b and one first flow passage 50 a arealternately arranged in parallel. In FIG. 14, the ground line of thesecond electrode 52 is not shown.

According to the modified embodiment of FIG. 14, a large reaction areafor reaction of the raw material gas and the plasmatized excitable gascan be obtained, the raw material gas can sufficiently be reacted toform into a film and the reaction efficiency (yield) can be enhanced.Moreover, by mildly blowing off the plasmatized excitable gas from therespective second flow passages 50 ab, a generally laminar flow statecan surely be obtained.

FIGS. 15 through 20 show a fourth embodiment of the present invention.

In the fourth embodiment, as in the first embodiment, second flowpassages are arranged on the left and right sides with a central firstflow passage sandwiched therebetween. Those three flow passages areconverged and continuous with a single common blowoff passage 25 a. Thefourth embodiment is different from the first embodiment in respect ofthe arrangement position of the ground electrode and the location of theplasma discharge part of the second flow passage.

More specifically, as shown in FIGS. 15 and 17, in the processing head 3of the fourth embodiment, dummy electrode spacers 52S instead of theground electrodes 52 of the first embodiment are disposed at thelocations for receiving the ground electrodes 52 of the first embodiment(FIGS. 3 and 6). The dummy electrode spacers 52S each have asubstantially same configuration as the ground electrodes 52 of thefirst embodiment, but they are composed of an insulative member(dielectric member) such as ceramic instead of conductive metal.Accordingly, the flow passage 50 b between the dummy electrode spacer52S and the electric field impressing electrode 51 does not serve as aplasma discharge space. The excitable gas is allowed to pass through theflow passage 50 b without being plasmatized.

A lower plate 25 of the fourth embodiment has not only the function as abase material opposing member or blowoff port constituting member of theprocessing head 3 but also the function as a retaining member for theground electrode. That is, as shown in FIGS. 15 and 18, a pair ofshallow receiving recesses 25 e are formed in a lower surface of thelower plate 25 with a common blowoff passage 25 a sandwichedtherebetween. The recesses 25 e extend in the back and forth direction(i.e., a longitudinal direction). A ground electrode (i.e., secondelectrode body) 52A composed of an elongate thin metal conductive plateis fitted to each receiving recess 25 e. Owing to this arrangement, theground electrodes 52A are arranged in opposing relation (i.e., in anarranging direction orthogonal to the longitudinal direction) at theside (lower side, a first plasma generating surface) which is to befaced with the base material W of the electric field impressingelectrode 51. Accordingly, the communication passages (i.e., gaspassages along a passage direction orthogonal to the longitudinaldirection and to the arranging direction) 20 b between the two electricfield impressing electrodes 51 and the lower plate 25 serve as theplasma discharge spaces, respectively.

As shown in FIG. 20, plasma PL is disposed not only at the inside of thecommunication passage 20 b but also overflowed to the crossing part 20c.

In the lower plate 25 composed of a dielectric member such as alumina,the part covering the upper surface of the metal-made ground electrode52A and the part (i.e., blowoff passage 25 a forming part) along the endface on the blowoff passage 25 a side of the ground electrode 52A have arole acting as a solid dielectric layer of the ground electrode.

As shown in FIG. 20, the right side end face facing the common blowoffpassage 25 a of the left side ground electrode (metal main body) 52A isflush with the same side end face (right side end face) of the metalmain body 56 of the left side electric field impressing electrode 51.The left side end face facing the common blowoff passage 25 a of theright side ground electrode (metal main body) 52A is flush with the sameside end face (left side end face) of the metal main body 56 of theright side electric field impressing electrode 51. The end face on thecommon blowoff passage 25 a side of the respective ground electrodes 52Amay be expanded from the same side end face of the electric fieldimpressing electrode main body 56.

As shown in FIG. 15, the end face on the opposite side to the commonblowoff passage 25 a side of each ground electrode 52A is projected froma rear surface of the electric field impressing main body 56.

As shown in FIG. 16, the opposite end edges in the longitudinaldirection of the ground electrode 52A are in contact with the lowerframe 24 composed of a metal conductor. A ground line 4 b is allowed toextend from the rear end part (opposite side to the arrangement side ofthe power feed pin 40) of the lower frame 24 and grounded.

The ground electrode 52A may be constituted by forming a slit, whichserves as the blowoff passage 25 a, in a single elongate metalconductive plate.

The fourth embodiment is also different from the first embodiment inrespect of the solid dielectric layer construction of the electrode 51.

That is, as shown in FIG. 19, the solid dielectric layer of the electricfield impressing electrode 51 in the fourth embodiment is composed of acase 57 which is separately formed from the electrode main body (i.e.,first electrode body) 56 instead of a thermally sprayed film 59 (FIG. 3)which is integrally thermally sprayed on the electrode main body 56. Thecase 57 includes a case main body (i.e., a dielectric first case body)57 a composed of ceramic (dielectric member) such as alumina and glass,and a lid 57 b composed of the same material as the case main body 57 a.The case 57 extends long in the back and forth direction (i.e., thelongitudinal direction).

The case body 57 a includes an internal space of the same configurationas the electrode body 56. The case main body 57 a is open with aU-shaped cross section to a rear surface (surface on the opposite sideto the opposing side of the other electrode 51) thereof. The electrodebody 56 is removably received in the internal space of the case body 57a. As shown in FIG. 15, the dielectric case body 57 a is provided with aprotrusive end part 571 on a side of the opening thereof (i.e., thefirst opening defined by upper and lower protruded end parts). Theprotrusive end part 571 is protruded relative to the electrode body 56.The end surface of the protrusive end part 571 of the case body 57 a isblocked with the lid 57 b. Owing to this arrangement, the entire surface(including the first plasma generating surface) of the electrode body 56is covered with the solid dielectric layer composed of the case 57.

The lid 57 b is in removable relation with the case main body 57 a.

The case main body 57 a is formed, for example, at a front side endplate thereof with a hole 57 c for allowing a power feed pin 40 to beinserted therein.

As shown in FIG. 15, the right plate of the left (first) case body 57 ain which the left (first) electrode body 56 is received is thin at theupper side, thick at the lower side and formed at the intermediate partwith a step. The left plate of the right (second) dielectric case body57 a in which the right (second) electrode body 56 is received is thinat the upper side, thick at the lower side and formed at theintermediate part with a step. Owing to this arrangement, the gaspassage 50 a between the first and second case bodies 57 a, 57 a is widein width at the upper side and narrow in width at the lower side.

According to the fourth embodiment, the excitable gas coming from anexcitable gas source 2 is not plasmatized in the left and right flowpassages 50 b, 50 b but it is plasmatized (excited and activated) incommunication passages 20 b, 20 b which are located next to the passages50 b, 50 b. Since the excitable gas does not contain any film formingcomponent, a film is not adhered to the lower surface of the electrode51 or to the upper surface (communication passage 20 b forming surface)of the lower plate 25.

As shown in FIG. 20, the excitable gas plasmatized in the left and rightcommunication passages 20 b flows to a crossing part 20 c. Also, the rawmaterial gas coming from the raw material gas source 1 enters thecrossing part 20 c via the central flow passage 50 a. Owing to thisarrangement, the film raw material is reacted with the plasmatizedexcitable gas to generate a reaction product p which forms a film. Inaddition, the raw material gas also passes through the plasma PL whichis overflowed to the crossing part 20 c (the raw material gas flows verynear the plasma discharge space). By this, the raw material gas can beplasmatized directly and more reaction products p can be obtained. As aresult, film forming efficiency onto the base material W can beenhanced.

Since a ground electrode 52A (grounded conductive member) is interposedbetween the electric field impressing electrode 51 and the base materialW, arch can be prevented from falling onto the base material W and thus,the base material W can be prevented from being damaged.

Moreover, since the end face on the side facing the common blowoffpassage 25 a of the ground electrode 52A is flush with the same side endface of the electric field impressing electrode main body 56, electricfield can be prevented from leaking downward from the side end face ofthe common blowoff passage 25 a of the ground electrode 52A and arc canmore surely be prevented from falling onto the base material W. Thus,the processing head 3 can be brought close to the base material W andthus, the distance (working distance) between the processing head 3 andthe base material W can be reduced sufficiently and thus, the workingdistance can be made shorter than the short deactivating distance (forexample, 2 mm) of radical under normal pressure. Thus, the base materialW can surely be brought into place before the reaction product p isdeactivated. As a result, a film can be formed at a high-speed andreliably.

Since the electric field impressing electrode main body 56 is entirelyenclosed in a case 57 as a solid dielectric layer, abnormal electricdischarge can more surely be prevented from occurring.

In case a film is adhered to the case 57 of the electric fieldimpressing electrode 51, the electrode 61 is removed from the nozzlebody 21 for decomposition. At the time of decomposition, the power feedpin 40 can easily be withdrawn. Removing the lid 57 b from the case mainbody 57 a, the electrode main body 56 can easily be taken out. Since afilm is adhered only to the case 57, for example, only the case 57 isreplaced and the electrode main body 56 is put into a new case. By doingso, it is no more required to prepare a plurality of electrode mainbodies 56. The work for putting the main body 56 into a new case is alsoeasy.

On the other hand, with respect to the film-adhered case 57, attempt ismade to remove the film from the case 57 by dipping the case 57 in astrong acid, or by any other suitable means. This makes it possible tore-use the case 57, thus resulting in elimination of the waste ofmaterials. Since the case 57 is separately formed for each electrode 51,the work of maintenance can be conducted separately.

By composing the dummy electrode spacer 52S from a metal conductorinstead of a dielectric member and grounding the same, the spacer 52Scan be used as a ground electrode part together with the planarelectrode 52A. By doing so, the entire second flow passages 50 b, 20 bcan serve as a plasma discharge space. In this case, the groundelectrode 52S may be of the same dielectric case receiving constructionas the electric field impressing electrode 51.

In the individual blowoff construction of the second embodiment (FIG.11), each of the four electrodes 51, 52 may be of dielectric casereceiving construction.

FIG. 21 shows a modified embodiment of the ground electrode constructionin the fourth embodiment.

In this modified embodiment, the end face on the side facing the commonblowoff passage 25 a of each ground electrode (metal main body) 52A isset back from the same side end face of the metal main body 56 of theelectric field impressing electrode 51. The common blowoff passage 52 aforming surface of the lower plate 25 is generally flush with the sameside end face of the electric field impressing main body 56. However,the present invention is not limited to this. Instead, the commonblowoff passage 25 a forming surface may be indented near to the endface of the ground electrode 52A. That is, the width of the commonblowoff passage 25 a may be increased approximately to the distancebetween the opposing end faces of the left and right ground electrodes52A.

According to this modified embodiment, a lateral electric field isformed by displacement between the electric field impressing electrodemain body 56 and the ground electrode main body 52A. This lateralelectric field causes the plasma PL to move around the lower side of theexpanding part 25H from the electrode 52A of the lower plate 25. Owingto this arrangement, further reaction of the raw material gas can betaken place at a location nearer to the base material W, and thus, afilm can be formed at a higher speed and reliably.

The entire surface of the ground electrode main body 52A is coated witha thin dielectric member 59A separately by suitable means. Owing to thisarrangement, abnormal electric discharge can more surely be preventedfrom occurring.

FIG. 22 shows a fifth embodiment of the present invention.

A processing head 3X of the fifth embodiment includes an electric fieldimpressing electrode 51X composed of a metal conductor, and a groundelectrode (grounded conductive member) 52X covering a lower part (sideto be faced with the base material W) of the electrode 51X. A soliddielectric member 28 composed of ceramic or the like is loaded betweenthe upper and lower electrodes 51X, 52X. The solid dielectric member 28is a solid dielectric layer which is common to the two electrodes 51X,52X. By this solid dielectric member 28, the two electrodes 51X, 52X areelectrically isolated. A cutout part 52 b is formed at a central part ofthe ground electrode 52X. A lower surface of the solid dielectric member28 is exposed from this cutout part 52 b.

Tip parts of two blowout nozzles 61, 62 are arranged at the side of theground electrode 52X. A basal end part of the raw material gas blowoffnozzle 61 (first flow passage forming means) is continuous with a rawmaterial gas source 1 through a raw material gas tube 1 a, and a basalend part of the excitable gas blowoff nozzle 62 (second flow passageforming means) is continuous with an excitable gas source 2 through anexcitable gas source 2 through an excitable gas tube 2 a. The blowoffshafts at the tips of those blowoff nozzles 61, 62 are diagonallydisposed toward a space between the ground electrode 52X and the basematerial W. Moreover, the excitable gas blowoff nozzle 62 is disposed atan upper side (nearer to the ground electrode 52X) of the raw materialgas blowoff nozzle 61.

According to the fifth embodiment, the excitable gas is blown off into aspace between the ground electrode 52X and the base material W from theupper side nozzle 62, and at the same time, the raw material gas isblown off into the same space from the lower side nozzle 61. At thattime, a generally laminar flow is formed in which the excitable gas isone-sided to the upper side and the raw material gas is one-sided to thelower side. The upper side excitable gas flows into the cutout part 52b.

On the other hand, a lateral electric field is taken place in the cutoutpart 52 b by pulse voltage impression of the pulse power source 4. Bythis, the inside of the cutout part 52 b serves as a plasma dischargespace, and the excitable gas flown into the cutout part 52 b isplasmatized (excited and activated). The raw material gas contacts thisplasmatized excitable gas. Or the raw material gas flows very near theplasma discharge space 52 b. By this, the raw material gas can bereacted right near the base material W, and a film A can be formed at ahigh speed and reliably. Since the excitable gas flow comes nearer tothe ground electrode 52X side than the raw material gas does even afterthe excitable gas passes through the plasma discharge space 52 b,adhesion of a film to the lower surface of the ground electrode 52X,i.e., the lower surface of the processing head 3X can be prevented orrestrained.

Since the ground electrode 52X (grounded conductive member) isinterposed between the electric field impressing electrode 51X and thebase material W, arc can be prevented from falling onto the basematerial W, and thus, the base material W can be prevented from beingdamaged.

FIG. 23 shows a sixth embodiment of the present invention.

In a processing head 3Y of the sixth embodiment, a paired electric fieldimpressing electrodes 51Y and ground electrodes 52Y are distantlyarranged leftward and rightward in opposing relation. A second flowpassage 20 h serving as a plasma discharge space is vertically formedbetween those electrodes 51Y, 52Y. A tube 2 a extending from theexcitable gas tube 2 is connected to the upper end part (upstream end)of the second flow passage 20 h.

A conductive member 29 composed of a metal plate is disposed at thelower end part of the processing head 3Y. The conductive member 29 isgrounded through a ground line 4 b. The conductive member 29 covers alower side (side to be faced with the base material W) of the electricfield impressing electrode 51Y. An insulative member 28Y forelectrically isolating the electric field impressing electrode 51Y andthe conductive member 29 is loaded between the electrode 51Y and themember 29.

A gap 20 g serving as a first flow passage is horizontally formedbetween the ground electrode 52Y and the conductive member 29. A tube 1a extending from the raw material gas source 1 is connected to a rightend part (upstream end) of the first flow passage 20 g. A left end part(downstream end) of the first flow passage 20 g is crossed with a lowerend part (downstream end) of the second flow passage 20 h. Theconductive member 29 is formed with a blowoff passage 29 a extendingfrom the crossing part 20 c between the first and second flow passages20 g, 20 h right thereunder. The blowoff passage 29 a serves as a commonblowoff passage for the raw material gas and the excitable gas.

Also in the sixth embodiment, adhesion of a film to the plasma dischargespace forming surfaces of the electrode 51Y, 52Y, etc. can be preventedfrom occurring, and arc can be prevented from falling onto the basematerial W from the electric field impressing electrode 51Y.

FIG. 24 shows a modified embodiment of an electrode powerfeeding/grounding construction. A covered conductor 46 serving as apower feed line 4 a or ground line 4 b is constituted by covering aconductive wire 46 a with an insulative tube 46 b. The coated conductor46 is inserted in a hole 56 d of an electrode main body 56 through ahole 57 d of a dielectric case 57.

In the wire 46 a of the covered conductor 46, only the terminal end partlocated at the innermost side of the hole 56 d is exposed from theinsulative tube 46 b, and the part located on this side in the hole 56 dis covered with an insulative tube 46 b. Of course, the wire 46 a iscovered at a part thereof located in the hole 57 d of the dielectriccase 57 and at a part thereof located outside the case 57 with theinsulative tube 46 b.

A screw (bolt) 47 is screwed into the electrode main body 56 in such amanner as to be generally orthogonal to the hole 57 d. By this screw 47,the exposed tip part of the wire 46 a is pressed against the innerperipheral surface at the innermost end part of the hole 57 d.

According to this construction, abnormal electric discharge from theconductor 46 can surely be prevented from occurring. Moreover, theterminal of the conductor 46 can surely be fixed to the electrode mainbody 56, so that the former can surely be electrically conducted withthe latter. Moreover, at the time of maintenance such as replacement ofthe dielectric case 57, the conductor 46 can easily be removed from theelectrode 51 by loosening the screw 47.

FIG. 25 shows a modified embodiment of the dielectric case serving as asolid dielectric layer of an electrode.

In the dielectric case 57X of the modified embodiment, an opening of thecase main body 57 a is formed on one end face in the longitudinaldirection, instead of the rear surface of the embodiment of FIG. 19. Ametal main body 56 of the electrode is inserted through this end faceopening. A lid 57 b of the case 57X covers up the end face opening.

FIGS. 26 and 27 show another modified embodiment of a dielectric case. Amain body 58X of this dielectric case 58 is constituted by combining apair of pieces 58 a, 58 b each having an L-shaped configuration insection. Those pieces 58 a, 58 b are formed at end edges thereof withpawls 58 c, 58 d, respectively. By fitting the pawls 58 c, 58 d withrespect to each other, a long square-shaped case main body 58X isformed. This case main body 58X is formed at opposite end parts thereofin the longitudinal direction with openings 58 e, respectively. A lid 58f is removably disposed at each of those openings 58 e.

FIG. 28 shows a further modified embodiment of an dielectric case. Inthis modified embodiment, two (a plurality of) electrode dielectriccases are integrally connected with each other. In other word, two (aplurality of) electrode metal main bodies 56 are received in a singlecommon dielectric case 70.

The common dielectric case 70 comprises a single case main body 71composed of a dielectric member, and two lids 74 composed of adielectric member. The case main body 71 includes two case main bodyparts 72 (i.e., dielectric first case body 72 and dielectric second casebody 72) horizontally extending long in mutually parallel relation, anda connection part 73 for interconnecting the opposite end parts (onlythe innermost side of the paper surface is shown in FIG. 28) of thosemain body parts 72. The rear surfaces on the opposite side to theopposing sides of those main body parts 72 are open with U-shaped crosssection. After the electrode metal main bodies 56 (i.e., first electrodebody 56 and second electrode body 56) are inserted in the main bodyparts 72 through those rear surface openings (i.e., the first openingdefined by upper and lower protruded end parts of first case body 72,and the second opening defined by upper and lower protruded end parts ofsecond case body 72), the rear surface openings are covered up by thelids 74, respectively.

In this embodiment, one of the two electrodes is an electric fieldimpressing electrode connected to a power source 4, and the other is agrounded ground electrode. However, the present invention is not limitedto this. Instead, they may be electrodes having the same polarities.

A flow passage 70 a (in this embodiment, a second flow passage servingas a plasma discharge space) is formed between two main body parts 72 ofthe common dielectric case 70. The flow passage 70 a extends long in thesame direction as the main body part 72. After being uniformized in thelongitudinal direction, the processing gas (excitation gas in thisembodiment) is guided into the upper end opening (upstream end) of theflow passage 70 a. The lower end opening of the flow passage 70 a servesas a blowoff port.

The dielectric case 70 constitutes a second flow passage forming means.The first flow passage forming means is not shown (the same is true alsoin FIGS. 29 through 33).

The upper side parts 72 c of the opposing side plates (i.e., soliddielectric layer on the opposing side of two electrodes) in two mainbody parts 72 are relatively thin, and the lower side parts 72 d arerelatively thick. A step 72 g is formed at an intermediate height. Owingto this arrangement, the upper side of the flow passage 70 a is large inwidth and the lower side is small in width as in the case with firstembodiment (FIG. 3).

The flow passage 70 a is made to serve as a plasma discharge space byelectric field impression of the pulse power source 4. This plasmabecomes relatively strong at the upper side (upstream side) of the step72 g and relatively weak at the lower side (downstream side) due todifference in thickness between the upper and lower plate parts 72 c, 72d serving as the solid dielectric layer. As apparent from the foregoingdescription, the state of plasma can be varied by changing the thicknessof the dielectric case.

The upper and lower plate parts 72 c, 72 d serving as the soliddielectric layer may be reversed in thickness in according with thepurpose.

In the embodiment of FIG. 28, since the dielectric cases of the twoelectrodes are integrally formed, the number of parts can be reduced.Moreover, the labor and time required for assembling the two electrodescan be eliminated, relative positioning of the electrodes can be madeeasily and correctly, and the shape dimension of the flow passage 70 canbe enhanced in precision.

The dielectric case construction itself disclosed in the fourthembodiment and in other various modified embodiments can be applied notonly to the electrodes for the use of a plasma film forming apparatusbut also to those electrodes for the use of other plasma surfaceprocessing apparatus such as cleaning and etching. In case of filmformation, the above-mentioned construction can also be applied to aconventional electrodes in which a mixed gas of a raw material gas andan excitable gas (for example, a mixed gas of silane and hydrogen) isguided to the plasma discharge space (the same is true to the modifiedembodiments that will be described hereinafter). In case, for example,the dielectric case 70 in the embodiment of FIG. 28 is applied to theconventional film forming system, generation of radical species ofhydrogen is restrained at the upper side part of the flow passage 70 a,and the radical species of silane can be relatively increased. And theradical species of hydrogen can be increased at the lower side part ofthe flow passage 70 a. In this way, the manner for generating theradical species can be changed in accordance with the flow, and thus,the surface processing recipe can be enriched.

FIG. 29 shows a still further modified embodiment of a dielectric case.In this dielectric case 70A, the opposing plates 72 b of two case mainbody parts 72 (i.e., dielectric first case body 72 and dielectric secondcase body 72) are slanted so as to be approached to each other towarddownward direction. Owing to this arrangement, the sectional area of theflow passage (i.e., the gas passage) 70 a is sequentially reduced towarddownward direction. The internal space of each case main body 72 isslanted and the opposing surfaces of the two electrode main bodies 56(i.e., first electrode body 56 and second electrode body 56) are slantedso as to be approached to each other toward downward direction. Owing tothis arrangement, the flow rate of the processing gas in the flowpassage 70 a and the state of plasma can sequentially be changed alongthe flowing direction (i.e., the gas passage direction), and the surfaceprocessing recipe can be enriched. It may be constructed such that theflow passage 70 a is gradually dilated along the flowing direction,depending on purposes.

FIGS. 30 and 31 show a yet further modified embodiment of a dielectriccase. The dielectric cases 57 for the left and right electrodes includea case main body 57 a for receiving therein the electrode main body 56,and a lid 57 b for blocking the rear surface opening as in the case withthe fourth embodiment. The dielectric case 57 extends long in the backand forth direction so as to match with the long electrode main body 56(FIG. 31).

Each dielectric case main body 57 a is integrally provided at an upperside thereof with a gas uniformizing part 80. A lower plate of the gasuniformizing part 80 and an upper plate of the case main body 57 a arecomposed of a common plate 84. The gas uniformizing part 80 is formedwith two upper and lower half-split expansion chambers 80 a, 80 bpartitioned with a horizontal partition plate 83.

The pair of left and right dielectric cases 57 with a gas uniformizingpart have a mutually reversal shape. The opposing edges of thedielectric cases 57 with a gas uniformizing part are abutted with eachother. Owing to this arrangement, the upper side half-split expansionchambers 80 a are combined with each other to form the first expansionchamber 81, and the lower side half-split expansion chambers 80 b arecombined with each other to form the second expansion chamber 82. Thoseexpansion chambers 81, 82 extend generally over the entire length of thegas uniformizing part-attached dielectric case 57 and thus, generallyover the entire length of the electrode and also enlarged in the widthdirection. Thus, the expansion chambers 81, 82 each have a sufficientlylarge capacity. Although the upper and lower expansion chambers 81, 82are same in capacity, they may be different.

The opposing edges of the upper plates of the pair of gas uniformizingparts 80 are abutted with each other, and provided at central partsthereof in the longitudinal direction with processing gas (excitable gasin this embodiment) receiving ports 80 c.

A narrow gap-like pressure loss forming passage 80 d is formed betweenthe pair of partition plates 83. The pressure loss forming passage 80 dextend generally over the entire length of the gas uniformizingpart-attached dielectric case 57. The upper and lower expansion chambers81, 82 are communicated with each other through the pressure lossforming passage 80 d.

A narrow gas-like introduction passage 80 e is formed between theopposing edges of a pair of plates 84. The introduction passage 80 eextends generally over the entire length of the gas uniformizingpart-attached dielectric case 57. The second expansion chamber 82 iscommunicated with the flow passage 50 b between a pair of case mainbodies 57 a through the introduction passage 80 e. The “gas uniformizingpassage” is constituted by the expansion chambers 81, 82 and thepassages 80 d, 80 e.

After introduced into the first expansion chamber 81 from the upper endreceiving port 80 c and expanded, the processing gas is throttled at thepressure loss forming passage 80 d to generate a pressure loss and thenintroduced into the second expansion chamber 82 and expanded again.Moreover, the processing gas is throttled again to generate a pressureloss. In this way, by applying expansion and throttling alternately, theprocessing gas can be introduced into the interelectrode flow passage 50a after it is sufficiently uniformized in the longitudinal direction. Bythis, a uniform processing can be conducted.

According to the gas uniformizing part integral type dielectric caseconstruction, the number of parts can be reduced.

The gas uniformizing part expansion chamber is not limited to two stagesof the first and second chambers 81, 82 but three or more stages may beprovided. The pressure loss forming passage 80 d which connects theexpansion chambers to each other may be formed in a plurality ofspot-like holes, instead of the above-mentioned lit-like holes, arrangedin the longitudinal direction.

FIGS. 32 and 33 show a yet further modified embodiment of a dielectriccase.

A dielectric case 90 for each electrode includes a case main body 91 forreceiving therein an electrode main body 56 and a lid 92 for blockingthe rear surface opening as in the case with the fourth embodiment. Asshown in FIG. 33, the dielectric case 90 extends long in the back andforth direction so as to match with the long electrode main body 56.

The upper side part of the opposing surface with respect to the otherelectrode in each of the left and right case main bodies 91 is formedwith a shallow tree-like groove 91 a, and the lower side part is formedwith a shallow recess 91 b. The tree-like groove 91 a is branched overplural stages so as to be spread in the longitudinal direction towarddownward direction from the central part of the upper end edge of thecase main body 91. The recess 91 b is continuous with the plural branchgrooves at the terminal of the tree-like groove 91 a. The recess 91extends generally over the entire length of the case main body 91 and iscontinuous with a lower end part of the case main body 91.

The left and right dielectric cases 90 are abutted with each other in apalms-put-together manner. Owing to this arrangement, the left and righttree-like grooves 91 a are jointed with each other to form a tree-likegas dispersing passage (gas uniformizing passage) 90 a, and the recesses91 b are jointed to form a gas blowoff passage 90 b. The passage 90 bextends generally over the entire length of the case 90 and thus theelectrode main body 56. The passage 90 b is continuous with all thebranch passages at the tail end of the tree-like gas dispersing passage90 a and open downward. Almost entire passages 90 a, 90 b are interposedbetween a pair of electrode main bodies 56.

The processing gas (excitable gas in this embodiment) introduced intothe upper end opening of the tree-like passage 90 a is sequentiallyshunted in the longitudinal direction through the tree-like passage 90 aand thereafter, guided into the passage 90 b. At the same time, theelectric field is impressed between a pair of electrodes by a powersource 4. By this, the processing gas is plasmatized not only in theshunting process of the tree-like passage 90 a but also in the passingprocess of the blowoff passage 90 b. Then, the processing gas is blownoff through the lower end opening of the blowoff passage 90 b. Thetree-like passage 90 a and the blowoff passage 90 b constitute the“plasma discharge space of the second flow passage”.

FIG. 34 shows a normal pressure plasma film forming apparatus M7according to a seventh embodiment of the present invention.

A processing head 3Z of the normal pressure plasma film formingapparatus M7 is constituted by vertically overlapping a gas uniformizingpart (not shown) and a nozzle part 20 as in the case with the firstembodiment.

The lower end part of the nozzle part 20 is provided with a lower plate101 (base material opposing member) which is to be faced with a basematerial W.

As shown in FIG. 35, the lower plate 101 has a rectangular horizontalplate-like configuration, in plan view, extending in the back and forthdirection. The lower plate 101 is composed of an insulative and porousceramic (gas permeating material). The pore diameter is, for example,about 10 μm, and the porosity is, for example, about 47%.

As shown in FIGS. 34 and 35, the width direction (short direction) ofthe lower plate 101 is more greatly expanded leftward and rightward thanthe lateral width of the entire electrode group consisting of fourelectrodes 51, 52. In the lower plate 101, the central part in the widthdirection corresponding to the electrode group serves as a blowoffregion 101R₁, and the opposite end parts in the width direction serve asa pair of expanding regions 101R₂.

As shown in FIGS. 34 through 36, an electrode receiving recess 25 c isformed in an upper surface (opposite side to the opposing surface withrespect to the base material W) in the blowoff region 101R₁ of the lowerplate 101. Lower end parts of the four electrodes 51, 52 are inserted inthis receiving recess 25 c. Three-lines of slit-like blowoff passages 25b, 25 a, 25 b are formed in the lower plate 101 in left and rightparallel relation. The passages 25 b, 25 a, 25 b reaches the lowersurface of the recess 25 c from the bottom of the recess 25 c andslenderly extends in the back and forth direction. Those blowoffpassages 25 b, 25 a, 25 b are in communication with the correspondinginterelectrode flow passages 50 b, 50 a, 50 b, respectively.

Grooves 101 b slenderly extending in the back and forth direction areformed in the upper surfaces of the left and right expanding regions101R₂ of the lower plate 101. The grooves 101 b are deeply recessedproximate to the lower surface of the lower plate 101. Owing to thisarrangement, the lower plate 101 is reduced in thickness at the groove101 b portion.

A small step 101 c is formed at the intermediate part in the depthdirection of the groove 101 b. A rod 102 (gas permeation prohibitingmember) and an angle plate 103 (partition) are hooked on this step 101c. The rod 102 is composed of a non-porous ceramic (gas permeationprohibiting member) and has a square configuration in section. The rod102 extends in the back and forth direction along the groove 101 b. Thisrod 102 is pressed against the inner side surface on the blowoff region101R₁ side of the groove 101 b (groove part 101 d as later described) onthe upper side from the step 101 c.

The angle plate 103 is composed of a punching metal (porous plate) whichis densely formed with a plurality of small holes 103 a of a diameter ofabout 1 mm. The angle plate 103 has a sufficiently larger gaspermeability than the lower plate 101 which is composed of a porousceramic. The angle plate 103 has an L-shaped configuration in sectionand slenderly extends in the back and forth direction along the groove101 b. The groove 101 b is partitioned into two upper and lower stagegroove parts 101 d, 101 e by a bottom side part of the angle plate 103.The lower stage groove part 101 e is larger in width than the upperstage groove part 101 d by an amount equivalent to no presence of therod 102 and has a large capacity.

In the angle plate 103, it is accepted that the small hole 103 a is notformed in the vertical piece part abutted with the rod 102. It is alsoaccepted that this hole-less vertical piece part is directly abuttedwith the side surface in the blowoff region 101R₁ of the groove part 101d and the rod 102 is eliminated.

A pair of side frames 104 having a horizontal U-shaped configuration insection for sandwiching the electrode unit 50 from left and right aredisposed at the upper side of the left and right expanding region 101R₂of the lower plate 101. The upper surface opening of the upper stagegroove part 101 d is blocked with this side frame 104. An O-ring 106 forsealing the upper stage groove part 101 d is disposed at the lowersurface of the side frame 104.

Moreover, inert gas introduction pipes 105 communicating with the upperstage groove part 101 d are disposed at the pair of side frames 104,respectively. This inert gas introduction pipe 105 is continuous with aninert gas source 5 through an inert gas passage 5 a. Inert gas such asnitrogen is reserved in the inert gas source 5. Although two inert gasintroduction pipes 105 are disposed at the processing head 3 in such amanner as to be away forward and backward, the present invention is notlimited to this. Three or more inert gas introduction pipes 105 may bedisposed at the processing head 3 in such a manner as to be away forwardand backward, or only one inert gas introduction pipe 105 may bedisposed at the center in the back and forth direction.

The “inert gas introduction means” is constituted by the inert gassource 5, the inert gas passage 5 a, the inert gas introduction pipe 105and the side frame 104 for blocking the groove part 101 d.

According to a normal pressure plasma film forming apparatus M7 of aseventh embodiment, as shown in FIG. 34, the processing gas flow apassed through the blowoff region 101R₁ is introduced between theexpanding region 101R₂ and the base material W. By this, a film A can beformed also on the base material W right under the expanding region101R₂. As a result, the film forming ratio of the raw material can beenhanced and loss can be reduced.

Concurrently with the film forming operation, the inert gas coming fromthe inert gas source 5 in introduced to the upper stage groove part 101d via the passage 5 a and the pipe 105. Thereafter, the inert gas passesthrough the small holes 103 a formed in the bottom side part of theangle plate 103. At that time, pressure loss occurs. Then, the inert gasis fed to the lower stage groove part 101 e and expanded. This makes itpossible to uniformize the inert gas in the back and forth longitudinaldirection.

Moreover, the inert gas permeates into the porous lower plate 101 fromthe inner peripheral surface (bottom surface and left and right sidesurfaces) of the lower stage groove part 101 e. And the inert gas oozesout, little by little, from the expanding region 101R₂ of the lowerplate 101. By this, the lower surface of the expanding region 101R₂ iscovered with a thin layer b of the inert gas. Owing to this inert gaslayer, the processing gas flow a can be prevented from directlycontacting the expanding region 101R₂ of the lower plate 101. As aresult, the expanding region 101R₂ of the lower plate 101 can beprevented from being adhered with a film. Particularly, since the lowerplate 101 becomes very thin at the groove 101 e portion, an inert gaslayer b can surely be formed thereunder and film adhesion can surely beprevented from occurring.

On the other hand, since the oozing amount of the inert gas is verysmall, the processing gas flow a is hardly disturbed. By this, the filmformation onto the base material W right under the expanding region101R₂ can surely be conducted. In addition, an amount of film formationonto the base material W can be increased by an amount equivalent to nofilm adhesion to the lower plate 101. As a result, the raw material losscan more surely be reduced, and film forming efficiency can further beenhanced.

Incidentally, the inert gas in the upper stage groove part 101 d isprevented from permeating into the blowoff region 101R₁ side by the rod102 which has absolutely no gas permeability. This makes it possiblethat the inert gas layer b hardly prevails on the blowoff region 101R₁.Accordingly, the processing gas flow a having many active species in theblowoff region 101R₁ is not disturbed nor diluted by the inert gas. Bythis, the film A formed on the base material W right under the blowoffregion 101R₁ can surely be improved in quality. On the other hand, inthe blowoff region 101R₁, since film adhesion onto a nozzle end piece101 hardly occurs, no inconvenience is encountered even if the inert gaslayer b is not formed.

It is accepted that the expanding region 101R₂ of the lower plate 101 iscomposed of a gas permeable material such as a porous ceramic, while theblowoff region 101R₁ is composed of a gas permeation prohibitingmaterial such as a non-porous ceramic.

The component member of the blowoff region 101R₁ and the componentmember of the expanding region 101R₂ may be composed of differentmembers. The component member of the expanding region 101R₂ may beconstituted by a horizontal frame (support means) for the processinghead.

The gas oozing construction of this embodiment may be applied to thecommon blowoff passage construction of the first and fourth embodiments.

FIG. 37 shows a normal pressure plasma film forming apparatus accordingto an eighth embodiment of the present invention.

The nozzle part 20 of the processing head 3A of the apparatus M8includes a holder 110 extending in the back and forth direction(orthogonal direction to the paper surface of FIG. 37), a side frame 112disposed as the side part thereof, and an upper plate 113 covering theirupper surfaces.

The upper plate 113 is constituted of two ceramic plates superimposedone upon the another. The upper plate 113 is provided thereon with afirst gas rectifier part 114. A tube 1 a from a first gas source (rawmaterial gas source) 1 is connected to the first gas rectifier part 114.Although not shown, a uniformizing passage 30 x constituted byvertically connecting a plurality of small holes scatteringly arrangedand a chamber, etc. extending in the back and forth direction, isdisposed within a stainless steel-made main body 114X of the first gasrectifier part 114. A lower end part of the uniformizing passage 30 x iscontinuous with a slit-like introducing passage 113 a which is formed ata central part in the left and right direction of the upper plate 113and elongated in the back and forth direction. After uniformized in theback and forth direction at the uniformizing passage 30 x, the first gas(raw material gas) coming from the first gas source 1 is introduced intothe introducing passage 113 a.

The side frame 112 of the processing head 3A is constituted byvertically overlapping a thick ceramic plate 112U and two metal plates112M, 112L which are formed of stainless steel, aluminum or the like. Aplurality of second gas receiving ports (only one is shown) 115 aredisposed on opposite sides in the left and right direction of theceramic plate 112U and separately arranged in the back and forthdirection. The tube 2 a from a second gas source (excitable gas source)2 is branched and connected to corresponding receiving ports 115. A thingap 112 a is formed between the ceramic plate 112U and the metal plate112M disposed under the ceramic plate 112U. Left and right end parts ofthis gap 112 a are continuous with the receiving port 115.

An electrode holder 110 of the processing head 3A is composed of aninsulative member such as ceramic. As shown in FIG. 38 on an enlargedscale, two left and right electric field impressing electrodes 51 aresupported by this holder 110.

Each electric field impressing electrode 51 includes a main body 56Hcomposed of a conductive metal such as stainless steel and aluminum, anda ceramic-make dielectric case 57 for receiving therein the metal mainbody 56H. The electrode 51 extends in the back and forth direction(direction orthogonal to the paper surface of Figures). The crosssection of the electric field impressing electrode main body 56Hexhibits a generally trapezoidal configuration in which a bottom surfaceof the main body 56H is slanted downward toward the center (the otherelectric field impressing electrode 51 side) in the left and rightdirection. All corners of the electric field impressing electrode mainbody 56H are rounded in order to prevent an arc discharge fromoccurring.

The dielectric case 57 includes a box-like case main body which is openat an upper surface thereof and elongated in the back and forthdirection, and a lid 57 b for blocking the upper surface opening of thiscase main body 57 a. A bottom plate of the case main body 57 a is verythin compared with the side plate and the lid 57 b. The bottom plate ofthis case main body 57 a is slanted downward toward the center (theother electric field impressing electrode 51 side) in the left and rightdirection. A slanted bottom surface of the metal main body 56H havingthe trapezoidal configuration in section is abutted with an inner bottomof the slanted bottom plate.

A ceramic-made spacer 135 is loaded above the metal main body 51H withinthe case main body 57 a.

Each electric field impressing electrode 51 is provided with a powerfeed pin 137. The power feed pin 137 vertically pierces through the lid57 b and the spacer 135 and is embedded in the metal main body 56H. Anupper end part of the power feed pin 137 is received in a recess 116 awhich is formed in an upper surface of the holder 110. As shown in FIG.37, a power feed line 4 a from a power source 4 is connected to an upperend part of each power feed pin 137. The recess 116 a is provided at anupper end opening thereof with a ceramic-make cap 117.

A first flow passage 50 a for the first gas is disposed between twoelectric field impressing electrodes 51, which is symmetrical in theleft and right direction, of the holder 110. The first flow passage 50 avertically extends over the entire length of the electrode 51 in theback and forth direction (direction orthogonal to the paper surface ofFigures). An upper end part (upstream end) of the first flow passage 50a pierces through the holder 110 and is continuous with the entirelength in the back and forth direction of the introducing passage 113 aof the upper plate 113. Eventually, it is continuous with the first gassource 1 through the uniformizing passage 30 x of the rectifier part 114and the tube 1 a.

Ceramic-made plates 118 are abutted with the surfaces on the first flowpassage side of each electric field impressing electrode 51 and theholder 110, respectively. The upper end part of the plate 118 reachesthe inner surface of the introducing passage 13 a. The pair of plates118 constitute the “first flow passage forming means”.

The processing head 3A is provided with ground electrodes 52 which aredisposed on the lower side of the electric field impressing electrodes51 such that each ground electrode 52 forms a pair with thecorresponding electric field impressing electrode 51. The left and rightground electrodes 52 are symmetrical with each other with the centralfirst flow passage 50 a sandwiched therebetween. Each ground electrode52 includes a main body 56E composed of a conductive metal such asstainless steel and aluminum, and a thin and planar plate 34 formed ofalumina or the like and serving as a solid dielectric layer of thismetal main body 56E. The ground electrodes 52 extend in the back andforth direction (direction orthogonal to the paper surface of Figures).

The ground electrode main body 56E includes a horizontal bottom surface(base material opposing surface), and a slant surface slanting towardthe center in the left and right direction such that the slant surfaceforms an acute angle with respect to this bottom surface. The groundelectrode main body 56E has a trapezoidal configuration in section. Thebottom surfaces of the main bodies 56E of the left and right groundelectrodes 52 are flush with each other.

As shown in FIG. 37, each ground electrode main body 56E is connected toleft and right outer side metal plates 112A, 112L. The metal plates112M, 112L are each provided at outer end faces thereof with a groundpin 138. A ground line 4 b extends from this ground pin 138 so as to begrounded. Owing to this arrangement, the ground electrode 52 isgrounded.

The inclination angle of the slant surface of the ground electrode mainbody 56E having a trapezoidal configuration in section is equal to theinclination angle of the slant bottom part of the upper side electricfield impressing electrode 51 which forms a pair together with theground electrode main body 56E. The solid dielectric plate 134 isabutted with the top of the slant surface of the ground electrode mainbody 56E. Of course, the solid dielectric plate 134 is slanted at anequal angle to that of the main body 56E along the slant surface of themain body 56E.

The “second flow passage forming means” is constituted by the electrodes51, 52. That is, one each of second flow passages 50 b serving as aplasma discharge space is formed between the vertically pairedelectrodes 51, 52 on the left side of the first flow passage 50 a, andbetween the vertically pairs electrodes 51, 52 on the right side of thefirst flow passage 50 a. Specifically, the space between the slantedbottom surface (first surface) of the case main body 57 a of theelectric field impressing electrode 51 and the slanted outer surface(second surface) of the solid dielectric plate 134 of the groundelectrode 52 on the lower side of thereof serves as the second flowpassage 50 b. Each second flow passage 50 b extends over the entirelength of the electrodes 51, 52 in the back and forth direction(direction orthogonal to the paper surface of Figures).

The upper end part (upstream end) of each second flow passage 50 b isconnected to the entire length in the back and forth direction of a gap112 a between the side frames 112 through a horizontal gap 154 betweenthe upper surface of the ground electrode 52 and the holder 110.Eventually, it is continuous with the second gas source 2 through thereceiving port 115 and the tube 2 a.

The left side second flow passage 50 b is slanted rightward downward insuch a manner as to approach the first flow passage 50 a incorrespondence with the slant surfaces of the left side electrodes 51,52. The right side second flow passage 50 b is slanted leftward downwardin such a manner as to approach the first flow passage 50 a incorrespondence with the slant surfaces of the right side electrodes 51,52. The inclination angles of the left and right second flow passages 50b are symmetrical with each other with the vertical first flow passage50 a sandwiched therebetween.

The lower end parts (downstream ends) of the left and right second flowpassages 50 b are crossed at one place with the lower end part(downstream ends) of the first flow passage 50 a at acute angles.Moreover, the crossing part among those three passages 50 b, 50 a, 50 bdirectly serves as a blowoff port 50 c. This blowoff port 50 c is opento a bottom surface of the processing head 3A which is constituted bythe left and right ground electrodes 52.

According to the normal pressure plasma film forming apparatus M8 of theeighth embodiment, the first gas coming from the first gas source 1 isintroduced into the central first flow passage 50 a via the tube 1 a,the uniformizing passage 30 x, and the introducing passage 113 asequentially in this order. Concurrently with this, the second gascoming from the second gas source 2 is introduced into the left andright second flow passages 50 b via the tube 2 a, the receiving port115, and the gaps 112 a, 154 sequentially in this order, and plasmatized(excited and activated) by being impressed with electric field, so thatactive species are generated.

When reached the blowoff port 50 c at the downstream end of the secondflow passage 50 b, the second gas thus plasmatized is converged with thefirst gas coming from the first flow passage 50 a. By this convergence,the raw material of film contacts the active species of the second gasand reaction is taken place therebetween. Simultaneous with theconvergence, i.e., simultaneous with the reaction taken place betweenthe raw material and the active species, those processing gases areblown off downward through the blowoff port 50 c. Accordingly, film ishardly adhered to the blowoff port 50 c. By blowing the processing gasagainst the base material W, a film such as poly-silicon (p-Si) isformed.

As described above, the contact between the ram material of film of thefirst gas and the active species of the plasmatized second gas occurs atthe same time the first and second gases reach the blowoff port 50 c andare blown off. Therefore, it is no more required to wait for scatteringafter blowoff. Thus, the active species are hardly deactivated and stillgood enough for taking place reaction. Particularly, even if theprocessing is made under normal pressure where the life of the activespecies is short, a sufficient reaction can be obtained. As a result, afavorable film A can be obtained and the film forming efficiency can beenhanced. Moreover, it is no more required to heat the base material Wup to a high temperature in order to enhance reaction, and a film cansufficiently be formed even at a normal temperature.

Since the second flow passage 50 b is crossed at an acute angle withrespect to the vertical first flow passage 50 a, the first and secondgases can surely be sprayed against the base material W while mixing thefirst and second gases so that they form a single flow. Thus, the filmforming efficiency can be enhance.

Moreover, the left and right second flow passages 50 b are symmetricallyarranged with the central first flow passage 50 a sandwichedtherebetween, it becomes possible that the second gas is uniformlyconverged to the left and right opposite sides of the first gas to forma single gas flow, so that the converged gas can be sprayed to the rightfront surface of the base material W. Thus, the film forming efficiencycan further be enhanced.

The present invention is not limited to the above-mentioned embodiments,but many changes and modifications can be made without departing fromthe spirit of the invention.

As a power source (electric field impressing means), a high frequencypower source may be used in which a high frequency electric field isimpressed between the first and second electrodes.

The present invention can be applied not only to a normal pressureplasma film formation conducted under generally normal pressurecircumstance, but also to a low pressure plasma film formation conductedunder reduced pressure.

It goes without saying that the present invention can be applied tovarious kinds of film formation such as a-Si, p-Si, SiN and SiO₂. Incase of film formation using a-Si and p-Si, SiH₄ is used for the firstgas and H₂ is used for the second gas. In case of film formation usingSiN, SiH₄ is used for the first gas and N₂ is used for the second gas.In case of film formation using SiO₂, TEOS or TMOS is used for the firstgas and O₂ is used for the second gas.

The electrodes 51, 52 of the first, second and seventh embodiments, etc.may be of the same dielectric case receiving construction as in the casewith the fourth embodiment (FIG. 19) and its modified embodiment (FIG.25, etc.)

It is also accepted that as the solid dielectric layer of the electrode51 of the fourth and eighth embodiments, etc., instead of the dielectriccase 57, a film is formed on the surface of the electrode main body 56by suitable means such as thermally spraying a dielectric member such asceramic thereon, or bonding a resin-made sheet such astetrafluoro-ethylene thereto.

In the dielectric case receiving construction, the lid of the dielectriccase may be rotatably connected to the case main body. The powerfeed/ground pin and the covered conductor may be pierced into theelectrode main body instead of the case main body through the lid.

The electric field impressing electrode may have a sleeve-like orannular configuration and its internal space may serve as the first flowpassage. The ground electrode may have a sleeve-like or annularconfiguration capable of coaxially receiving therein this sleeve-likeelectric field impressing electrode, and an annular space between thoseelectrodes may serve as the second flow passage.

The base material may be arranged above the processing head. In thatcase, the base material opposing member may preferably be placed on theupper end part of the processing head. The intake port 10 a of thehousing 10 is directed upward. The processing head 20 may be fixed tothe outer housing 10 by an easy attaching/detaching mechanism such as abolt or a hook.

The present invention is not limited that the first flow passage isconstituted by an electric field impressing electrode disposed betweentwo electric field impressing electrodes, but the first flow passage maybe constituted by a specific first flow passage forming member such as anozzle body and a tube.

In the eighth embodiment, it is accepted that the second flow passage isvertically arranged with respect to the base material opposing surfaceand the first flow passage is diagonally arranged. It is also acceptedthat only one second flow passage is disposed at the center and twofirst flow passages are arranged on its opposite sides. The first andsecond flow passages and electrodes may not only be linearly extended inthe back and forth direction but they be also be, for example, annularlyarranged in section. One of the electric field impressing electrode andthe ground electrode may annularly surround the other electrode. In thatcase, the first flow passage may be formed within the inner sideelectrode, and the annular space between the inner and outer electrodesmay serve as the second flow passage. It is also accepted that one ofthe first and second flow passages is concentrically arranged in such amanner as to approach the other passage downward with the other passageplaced therebetween.

INDUSTRIAL APPLICABILITY

The present invention can be utilized, for example, as a plasma CVD withrespect to a semiconductor base material.

1. A plasma surface processing apparatus for processing a surface of anobject to be processed with a processing gas plasmatized under anelectric field applied from an electric power source, said apparatushaving an electrode structure having a gas passage through which saidprocessing gas is passed from an upstream side to a downstream side of apassage direction and for generating said electric field in said gaspassage, said electrode structure comprising: an elongate metallic firstelectrode body that is longer in a longitudinal direction orthogonal tosaid passage direction and shorter in the passage direction, the firstelectrode body having an elongate outer first surface which is a flatsurface crossing with an arranging direction orthogonal to both thepassage direction and the longitudinal direction and which is longer insaid longitudinal direction and shorter in the passage direction; anelongate metallic second electrode body that is longer in saidlongitudinal direction and shorter in the passage direction, said secondelectrode body being arranged in parallel with said first electrode bodyin the arranging direction, said second electrode body having anelongate outer second surface which is a flat surface crossing with thearranging direction and facing said first surface in said arrangingdirection and which is longer in the longitudinal direction and shorterin the passage direction, one of said first and second electrode bodiesbeing connected with said electric power source, the other of said firstand second electrode bodies being electrically grounded, said electricfield being generated between said first and second surfaces; and anelongate dielectric first case body that is longer in said longitudinaldirection and shorter in the passage direction, said first case bodybeing arranged in parallel with said first and second electrode bodies,said first case body being formed a cross section orthogonal to saidlongitudinal direction into a U-shape so that said first case body has afirst internal space and a first opening, a side of the first internalspace nearer to the second electrode body in the arranging direction andboth the upstream and the downstream sides of the first internal spacein the passage direction being surrounded by the first case body and aremaining side of the first internal space farther from the secondelectrode body in the arranging direction being opened to an outside andprovided as the first opening, a plane of the first opening is parallelto the longitudinal direction, said first electrode body being receivedin said first internal space so that said first surface is contactedwith an inner peripheral surface of said first case body, said secondelectrode body being disposed outside the first internal space of saiddielectric first case body in said arranging direction, said firstopening facing away from said second electrode body, said gas passagebeing formed between said dielectric first case body and said secondelectrode body, said gas passage being longer in the longitudinaldirection and shorter in the passage direction, a first end of the gaspassage on the upstream side of the passage direction being connectedwith a source of the processing gas, a second end of the gas passage onthe downstream side of the passage direction being connected with ablowoff aperture, and an end part on a side of said first opening of aportion of said first case body on the downstream side of the firstinternal space being protruded in said one remaining side farther fromthe second electrode body in the arranging direction relative to saidfirst electrode body.
 2. An electrode structure according to claim 1,further comprising: an elongate lid made of a solid dielectric materialfor closing said first opening, said lid having a longer lengthdimension in the longitudinal direction and a shorter width dimension inthe passage direction, an end part on the downstream side of said lidcovering an end surface of said protruded end part in a location moreforward in said one remaining side farther from the second electrodebody in the arranging direction from said first electrode body.
 3. Anelectrode structure according to claim 1, wherein said electrodestructure further comprises: an elongate dielectric second case bodythat is longer in said longitudinal direction and shorter in the passagedirection, said second case body being arranged in parallel with saidfirst case body in said arranging direction, said second case body beingformed a cross section orthogonal to said longitudinal direction into aU-shape so that said second case body has a second internal space and asecond opening, both the upstream and the downstream sides of the secondinternal space in the passage direction and a side of the secondinternal space nearer to the first electrode body in the arrangingdirection being surrounded by the second case body, and an opposite sideof the second internal space farther from the first electrode body inthe arranging direction being opened and provided as the second opening,said gas passage being defined between said first and second casebodies, said second electrode body being received in said secondinternal space so that said second surface is contacted with an innerperipheral surface of said second case body, and an end part on a sideof said second opening of a portion of said second case body on thedownstream side of the second internal space being protruded in saidopposite side farther from the first electrode body in said arrangingdirection relative to said second electrode body.
 4. An electrodestructure according to claim 3, wherein said first dielectric case bodyand said second dielectric case body are separately formed.
 5. Anelectrode structure according to claim 4, wherein said first dielectriccase body has an opposing surface abutted with said second dielectriccase body, and said opposing surface is provided with a recess to serveas said gas passage.
 6. An electrode structure according to claim 3,wherein said first dielectric case body and said second dielectric casebody are integrally connected to one another.
 7. An electrode structureaccording to claim 3, wherein flow passage sectional area of said gaspassage varies along said passage direction.
 8. An electrode structureaccording to claim 3, wherein said first dielectric case body has aplate defining said gas passage, and a thickness of said plate variesalong said passage direction.
 9. An electrode structure according toclaim 3, wherein a distance between said first electrode body and saidsecond electrode body varies along said passage direction.
 10. Anelectrode structure according to claim 3, wherein said first dielectriccase body is provided with a gas uniformizing passage for dispersingsaid processing gas uniformly in said longitudinal direction and forintroducing said processing gas into said gas passage.